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THE PANTHEON EXPLAINED - Page 2

Pantheon front portico on a rainy day showing many people walking in front of the structure in the year 2018

The Pantheon Portico on a rainy day in 2018
Thank you to Deb Nystrom for the image

To jump to a specific topic, please use guide below or keep scrolling and explore.

PANTHEON PAGE 2 GUIDE

Welcome to Page 2 of the Roman Pantheon section. On this page, I explore the Pantheon floor's tile patterns, construction, restoration, and unique drainage system that copes with rain entering through the oculus. I will also explain how only one-third of the Pantheon floor tiles are the originals.

The three Pantheon interior floor tile patterns

Also explored is the Pantheon's wide columned entrance area known as the Portico, its floor patterns, and the surrounding ground level that changed so much over the centuries. Additionally, I will take a fascinating look at the Portico's ancient roof truss supports that held up its roof for 1,500 years.

These roof supports, built by the Romans, were composed of enormous solid bronze girders and rivets that, unfortunately, were all melted in the 1600s and replaced with the wooden ones we see today. I will show the only surviving piece of those bronze girders - one super-sized Pantheon bronze rivet.

Many aspects of the enormous Bronze Doors standing in the front entrance area are examined, including the amazing fact that the Pantheon's doors are the original ones dating from 128 AD - recent scientific analysis proves this.

Pantheon door close-up

The large Latin inscription above the columns is examined. Furthermore, I will explain how there is another Latin inscription, much smaller in size but containing many more words, below the large inscription. I will also show you where a serious Pantheon architectural error can be spotted - if you know where to look for it.

Large inscription on the front of Pantheon

Finally, the often neglected rear part of the Pantheon - its history and function - is discussed, along with the history of Pantheon flooding over the many centuries that damaged its floors as recently as 1937.

THE PANTHEON FLOOR

In many ways, the Pantheon floor seen today closely resembles the ancient floor because its patterns, colours, and stone types are exactly the same. However, in 1873 work on the floor was done which involved "restoration and relaying of the stones," which I explore in detail after the next two images.

Pantheon floor showing a couple standing on a marble floor tile which shows how large and beautiful the marble tiles are

People standing on the large Pantheon floor tiles
Thank you to rome101 for image

The floor looks amazing, and the geometric circles and squares are quite large. Standing inside the Pantheon and looking at that beautiful and wide floor, a huge dome, and the surrounding architecture really gives you a good sense of how splendid Roman buildings could be. Making the Pantheon's rotunda floor look good takes ongoing work, as shown in this photo of people restoring the floor as recently as 2006 (click to view).

Closeup photo of the Pantheon marble floors showing great detail

Close-up scan of Pantheon floor showing four types of stone
The colour scheme is white, gray, red, yellow
Image licensed from Alamy

The photo above looks more closely at a wide swath of the floor so you can notice the details of the various marbles and granite. The whole floor is made of stone tiles of very large proportions. There are four types of stone used: white marble with bluish-purple veins (Pavonazzetto), reddish-purple stone (Porphyry), dark gray granite, and a yellowish marble (Giallo Antico). The pattern is a mix of circles and squares, creating a simple but impressive pattern over the entire surface. This is a floor pattern that was used often by the Romans in their basilicas, bathhouses, and temples. Further down the page, I explore the Pantheon's floor pattern in more detail.

THE PANTHEON FLOOR IS ONLY 1/3 ORIGINAL

Pantheon floor showing a close view of the large tiles, specifically the center tile that shows it quite faded and discolored
and thus ancient

The middle tile's yellow marble has very faded areas that indicate it is ancient, whereas the vivid yellow tile in the upper left is probably a recent replacement - 2011

Image courtesy: Helen Simonsson - CC BY-SA 2.0

In the 1990s, an Italian Architect, Mario Lolli Ghetti, Director of Architecture & Fine Arts for the Italian Government, made numerous technical analyses and architectural inspections while doing restoration work in the Pantheon. His findings made clear the full extent of previous restoration work in the 1600s and 1700s. It is now apparent that two-thirds of the Pantheon floor is not original. The following quote gives good insight into the Pantheon floor situation:

In Lolli Ghetti's estimation, roughly two-thirds of the floor is either modern or ancient material that has been relaid in modern times.

Here and there are stones not known to antiquity, such as pieces of Giallo Senese marble from the environs of Siena, which replaced damaged portions of the more fragile Giallo Antico.

Nonetheless, the general pattern of the pavement and its polychromy have been faithfully maintained

The Pantheon: From Antiquity to the Present, page 1, Cambridge University Press, 2015

According to the information above, the patterns and colours of the Pantheon's floor tiles have been faithfully maintained despite much restoration work. Thus, the floor of the Pantheon's Rotunda strongly resembles the ancient floor Romans saw in 128 AD.

It truly is fascinating how people have used this ancient building for almost 2,000 years - the Pantheon is a direct connection to the Roman past. I sometimes wonder how a civilization capable of building such marvels could have allowed itself to collapse.

When Rome fell, an incredible amount of great architecture, art, knowledge, and people were lost - such a massive investment of time, money, resources, and skill was lost to us.

TIME & FLOODS ARE UNKIND TO MARBLE FLOORS

Because the Pantheon floor tiles are 1,900 years old, it is not surprising that many of them became discoloured, cracked and damaged to the point where replacement was necessary. These floor tiles had to cope with centuries of flooding, water damage, and the wear and tear that comes from millions of people walking on them.

Not only did flood water and mud enter the Pantheon through the front doors, but it also rose through the floor drain below the oculus due to sewers backing up. And after many years of flooding, thick sediments built up on the floors, which loosened some of the tiles. My drawing below shows how I imagine the Pantheon looked in the Dark Ages.

My drawing showing the Pantheon interior in the early Middle Ages when the floor was covered with mud and floor tiles were shifted,
discolored and broken due to regular flooding - this is a 'touchofrome.com' original image'

THE PANTHEON INTERIOR IN THE DARK AGES
- Floods, mud, and mould -

If you could travel back in time to the Dark Ages to enter the Pantheon, you would see a shocking sight - piles of mud, mould, and a damp and dank interior, with plants growing in the muck. Here and there, you would see floor tiles tilted to one side and buckling. And you can imagine the filth clinging to all the lower surfaces of the walls and columns. The flooding that caused these problems is discussed at the bottom of this page.

Though the Pantheon was converted into a church in the 7th century, this did not mean the interior was always kept clean and in a good state of repair. The building had numerous problems caused by centuries of change to the topography surrounding it.

As discussed on page one of the Pantheon section, in the year 1705 AD, someone cleaned a small part of a column inside the Pantheon, thus revealing beautiful yellow marble behind the muck. People were so surprised that Pope Clement XI and several Cardinals rushed to the Pantheon to behold this amazing sight.

Pantheon surrounded by water from flooding. This photo is a color reproduction

The Pantheon has been damaged by floods many times

This gives you an idea of how filthy the inside of the Pantheon was before the 1700s, in addition to how little was actually done to clean, repair, or restore the interior. My drawing above of a Pantheon with a build-up of mud and buckling floors, is probably close to the reality.

For those wondering why the upper part of the Pantheon walls are different, it is because the wall surfaces above the columns were completely rebuilt in a different way from the ancient and original porphyry panels.

Yes, the Pantheon floor looks very good today because of much restoration. It would have taken a miracle to ensure that all the ancient floor tiles survived intact into the 21st century. Because many of the Pantheon's floor tiles did not survive, we have to thank all those people, over the last few hundred years, who spent the time and money to restore the Pantheon floor to its former glory for us to enjoy today.

THE PANTHEON FLOOR PATTERNS

Diagram showing Pantheon floor tile patterns, colors, and marble type - based on an actual photo of whole floor taken by a drone
hovering high above the floor

The Pantheon Floor's patterns and colours

The above image shows the patterns and colours found on the Pantheon floor. This image is quite accurate and can be compared to an actual photo (below) of the Pantheon floor as seen from directly above by a drone.

Notice how the diagonal patterns of gray circles and red circles are not always consistent. A diagonal line of gray circles sometimes ends with a red circle. Four different kinds of marble and granite stones were used to construct a series of patterns based on four colours: white, red, grey, and yellow. The image below is one of the images I used to create my Pantheon floor pattern and colours diagram.

Drone photo of whole interior Pantheon floor from high above

Photo of Pantheon Floor from top of ceiling
Dots are people and the long brown shapes are church pews

THE PANTHEON DOORS

photo of Pantheon doors which are open and showing Pantheon interior and oculus

The magnificent bronze Pantheon Doors

Photo courtesy (modified): jev55 - CC BY-NC 2.0

These immense double doors, made of solid bronze, date back to the 2nd century AD when the Pantheon was built. They are 7.3 metres high (24 feet) (according to brittanica.com) and weigh over 20.3 Metric Tonnes each (22 Tons USA/Canada).

Grooved bronze pilasters are located on either side of the doors, which are attached by two pins, one at the bottom and one at the top, and not by hinges. These pins allow the doors to rotate. The top pin fits into an architrave located above the door and below the perforated bronze grille. The lower pin fits into the floor. The image below shows the pin placement at the top of the door.

Diagram showing where top door pin for attachmenet and rotation of Pantheon doors is located

Image showing top pin position in a Pantheon door

The Pantheon doors have more of a brownish colour or patina instead of the typical "blue/green" hue of other bronze Roman doors that also have survived. When the 90% copper content in bronze oxidizes, the resultant patina can vary in colour, becoming either blue, green, brown, black, or even reddish. And thus, in the case of the Pantheon, the colour of its doors is brown.

ARE THE PANTHEON DOORS ORIGINAL?

Three things are said about the origins of the Pantheon's doors:

1	Some say that the doors are replacements and not ancient at all.
2	Others say that the doors are ancient but not the original ones.
3	Some believe, as do I, that the Pantheon's doors are both ancient and the original doors dating from the early second century.

photo of a Pantheon door opened and resting entirely inside the Pantheon

Pantheon door opened into the inside - 2012

Image courtesy: Jeff & Neda Fields - CC BY-NC-ND 2.0

Yes, the Pantheon doors we see today are indeed the original ones that date back to 128 AD and are not replacements. Unfortunately, there has been an ongoing misconception that the Pantheon's doors are "too small" to be the originals.

The Pantheon is one of only three ancient Roman buildings whose original doors have survived. However, the Pantheon doors' appearance was partially altered in 1563-65, when Pius IV had them undergo a restoration during which extensive cleaning was done and additional decorations, such as new bolts and Christian motifs, were affixed.

The following quote, from a Wikipedia article about the Pantheon, sums up very well the actual origins and status of these magnificent doors.

The large bronze doors to the cella, measuring 4.45 metres (14.6 ft) wide by 7.53 metres (24.7 ft) high, are the oldest in Rome.[49] These were thought to be a 15th-century replacement for the original, mainly because they were deemed by contemporary architects to be too small for the door frames.[50] Later analysis of the fusion technique confirmed that these are the original Roman doors,[49] a rare example of Roman monumental bronze surviving, despite cleaning and the application of Christian motifs over the centuries.

WIKIPEDIA
[49] Pantheon, Storio e Futura (History & Future) - Marco De Carolis, Siro Cinti, Etc. 2007 - Gangemi Editore
[50] Amanda Claridge, Rome - 1998 - Oxford University Press

In my opinion, this quote makes it clear that the Pantheon's bronze doors are the correct size as designed by the original Roman architects in the early second century. Furthermore, though the doors have indeed been cleaned and cosmetically altered, they are still the original doors that have simply been "spruced up" over the centuries.

I discuss this topic in much greater detail, with more supporting quotes, discussion points, and images in an additional section. If you are interested in more information regarding why the Pantheon's huge bronze doors are indeed the original ones made in 128 AD, then please click this link .

ARE THE PANTHEON DOORS MADE OF SOLID METAL ?

Recently, I read a statement by someone commenting on the makeup of the Pantheon doors. He claims they are not made of solid bronze but are made of a thick wooden core with bronze plates affixed by studs. I find this hard to accept because, to my knowledge, monumental Roman doors were always made of solid metal, as confirmed by the Encyclopaedia Britannica, see quote below:

... the Romans characteristically used solid bronze double doors. They were usually supported by pivots fitted into sockets in the threshold and lintel. The earliest large examples are the 24-foot (7.3-metre) double doors of the Roman Pantheon.

Listed below are other considerations regarding whether or not the doors are made of solid bronze, a metal that weighs 540 pounds (245 kg) per cubic foot. For this discussion, US/Canada TONS (2,000 pounds per Ton) are used, which is 90% of a Metric Tonne: 10 Tons = 9 Metric Tonnes:

•	Each door weighs 22 tons / 20 Metric Tonnes which would not be the case if the doors were primarily made of wood. Even oak, one of the heaviest woods at 50 lbs (22.6 kg) per cubic foot, weighs less than a tenth of bronze at 540 lbs (245 kg) per cubic foot, as shown in this chart;
•	Even if a Pantheon door was made of 20% bronze plating & bolts and rivets (4.5 tons) and 80% oak wood (1.5 tons), it would have a total weight of 6 tons, just over a quarter of the actual 22-ton weight of one door. Based on the simple mathematics, given the doors' size, thickness and weight, it seems far more likely that the Pantheon doors are made of solid bronze and not mostly wood.
•	After 1,900 years of time and regular flooding, as well as humidity, mould, and simple wear and tear, I doubt that any Pantheon doors made chiefly of wood would have survived, even with bronze plating on the surface for protection.

Photo closeup of Pantheon door front and looking up at a steep angle - with focus on door height, weight and door decorations
and bolts and rivets

24 feet of thick solid bronze
Image courtesy: Anthony Majanlahti CC BY-2.0

THE PANTHEON INSCRIPTIONS

The Pantheon facade contains two inscriptions. There is a much smaller but very long inscription below the large and prominent inscription seen in the photograph below.

1. THE MAIN INSCRIPTION:

Photo of Pantheon front portico with close-up of M AGRIPPA LF COS TERTIVM FECIT inscriptions and upper columns, entablaturem
and tympanum

The Pantheon's Main Inscription

Image courtesy: Old_Man_Leica - 2006 - CC BY-NC-2.0

Written across the Pantheon's frieze in bold letters, the Latin words below are seen, with the English translation underneath.

M • AGRIPPA • L • F • COS • TERTIUM • FECIT

MARCUS AGRIPPA, SON OF LUCIUS, CONSUL 3 TIMES, BUILT THIS

For centuries, this famous inscription on the front of the temple caused confusion regarding who actually had built the Pantheon. Understandably, everyone took the frieze inscription at face value and thus believed that Marcus Agrippa had built the Pantheon we see today. However, it took until almost the 20th century to discover who had constructed the Pantheon we see today.

The actual builders of this third version of the Pantheon were emperors Trajan, who began the construction, and Hadrian, who completed the work. Hadrian humbly gave credit for building the Pantheon's third version to Marcus Agrippa, who had built the first version of the Pantheon 150 years earlier. This noble act, unfortunately, caused confusion for later historians.

2. THE LOWER INSCRIPTION:

Right below the large inscription on the front of the Pantheon is another inscription that you can miss seeing because the letters are much smaller and are lightly engraved into the marble entablature. In the image below, you can see a closeup of the second inscription below those large bronze letters - but parts of it are damaged and can be hard to read.

I have provided the complete Latin text as well as the English translation below the image. Reminder: The ancient Roman alphabet did not use the letters "U" or "J" and instead used "V" for "U" and "I" for "J." Thus, the word AUGUSTUS was written as "AVGVSTVS" and the word JULIUS as "IVLIVS." The letter "W" also did not exist before the Middle Ages when the letters "U" and "I" were also added.

photo of Pantheon lower inscription beneath the main large inscription on the front of the building

Second Pantheon facade inscription below main inscription

IMP • CAES • L • SEPTIMIVS • SEVERVS • PIVS • PERTINAX • ARABICVS • ADIABENICVS • PARTHICVS • MAXIMVS • PONTIF • MAX • TRIB • POTEST • X • IMP • XI • COS • III • P • P • PROCOS ET IMP • CAES • M • AVRELIVS • ANTONINVS • PIVS • FELIX • AVG • TRIB • POTEST • V • COS • PROCOS • PANTHEVM • VETVSTATE • CORRVPTVM • CVM • OMNI • CVLTV • RESTITVERVNT

EMPEROR CAESAR LUCIUS SEPTIMIUS SEVERUS PIUS PERTINAX VICTOR OF ARABIA, ADIABNE, PARTHIA AND PONTIFEX MAXIMUS, TRIBUNE 10 TIMES, PROCLAIMED EMPEROR 11 TIMES, THREE TIMES A CONSUL, AND FATHER OF THE COUNTRY, PROCONSUL AND EMPEROR CAESAR MARCUS AURELIUS ANTONINUS PIUS FELIX AUGUSTUS, TRIBUNE FIVE TIMES, CONSUL, PROCONSUL, CAREFULLY RESTORED THE PANTHEON WHICH HAD BEEN DAMAGED BY AGE.

WHY IS THERE A SECOND INSCRIPTION?

In the year 202 AD, Emperor Septimius Severus and his son, Caracalla (Marcus Aurelius Antoninus), paid for repairs and restoration to the Pantheon. In recognition of their efforts, a long inscription was carved below the main inscription. Very likely, the engraved letters also would have been painted a colour, such as red, to make them much more noticeable. In the translation above, you can see all the honours and tributes to Emperor Severus - who does not seem to have been quite as humble as Emperor Hadrian.

3. PANTHEON LETTERS ARE METAL AND NOT PAINTED

The letters seen today are actually made of bronze, just like the original letters, which were made of gilded bronze. The close-up image below clearly shows that the letters are indeed made of metal and are not just painted on.

photo of closeup photo of Pantheon inscription's bronze letters showing that these letters are made of metal

Closeup of bronze letters of the Pantheon inscription.

During the dark centuries after the fall of the Western Roman Empire in 476 AD, bronze and other metals became rare and were thus much prized and looted - thus, the letters have been replaced, most recently during the Pantheon restorations in the 1890s.

Many inscriptions on ancient Roman arches and temples also had bronze letters. Looking at some of those inscriptions, one can still see tell-tale holes made by the pins and nails that attached the bronze lettering to the stonework.

closeup of holes where metal letters were attached by pins to the Arch of Constantine in Rome

Bronze letter pin holes on Arch of Constantine

You can see an example of those pin holes in the image above of the Arch of Constantine in Rome. Look closely at the "M", the "C", and the "A," where you can clearly see holes where letters were fastened with metal pins before they were pried off and looted over the centuries.

APRIL 21ST IN THE PANTHEON

The Pantheon was designed so that, one day each year, on April 21st at midday, the bright light from the oculus shines directly on the doorway entrance like a powerful spotlight. April 21 was an exceptional day to the ancient Romans because, in 753 BC, Roman mythology says the city of Rome was founded by twin brothers Romulus and Remus, sons of Rhea Silvia and Mars, the Roman god of War.

two photos of sunlight inside Pantheon heading towards the main Pantheon entrance on April 21

April 21 - light from the oculus moves towards the entrance

photo of sunlight filling Pantheon doorway at noon on April 21

Noon - April 21st - Pantheon entrance is filled with sunlight

It is said that the Emperor would stand in the doorway on that special day in April, and the effect was magical when the massive bronze doors swung open at noon to the crowds waiting outside. The ancient Romans were surely dazzled by the sight of the Emperor standing in that huge doorway, bathed in the brilliant light pouring out of the Pantheon. This ancient and magical event (minus the Emperor, of course) is something you can still behold if you happen to be in Rome on April 21st.

The arch above the door is the same width as the oculus, and the light travels at a 60-degree angle, illuminating the Pantheon doorway on one particular day of the year only. Such architectural precision is another example of the brilliant Roman engineering involved in the Pantheon's building process.

THE PANTHEON PORTICO

large photo of Pantheon portico, with Pantheon in sepia and background in black and white

The Portico of the Pantheon
Image courtesy: Miwok - Public Domain

The Pantheon Portico, like every other part of the Pantheon, has undergone many changes, deprivations, and restorations over its 1,900-year existence (128-2021 AD). One of the worst deprivations was the incomprehensible destruction, in 1625, of the ancient and huge bronze roof truss supports that held up the Pantheon Portico roof.

I will attempt to list all the significant changes the Pantheon Portico has endured since 128 AD, the year it was completed:

Pantheon Portico: 1,900 Years of Change

	It has changed from elevated above the ground to below and is currently level with the ground.
	Three of its original columns are gone, replaced with others from Roman Baths and a Villa.
	The bronze eagle and wreath housed within the tympanum are long gone, leaving behind only a series of connect-the-dot holes that whisper to us of a former glory lost to the ages.
	The giant statues of Emperor Augustus and his son-in-law Marcus Agrippa housed in the large niche spaces on either side of the entrance are long gone.
	The capitals atop its original thirteen columns are worn - the result of weather, time, and perhaps some human damage.
	The gilded bronze tiles atop the portico roof were removed in the 7th century, along with the bronze tiles that covered the Pantheon rotunda dome.
	And, most sadly, as mentioned at the start of this section, all the huge bronze trusses that weighed 152 tons / 138 Metric Tonnes* and which held up the Portico roof are all gone - melted down in order to produce cannons for the Castel Sant'Angelo in 1625. In the next section, I will discuss, at length, what happened to the huge bronze roof trusses, why it happened, and the wooden solution to holding up the Portico roof. * B. & D. Heinzelmann, "The metal roof truss of the Pantheon's portico in Rome -152 tonnes of bronze", Jan. 2018.

FROM BRONZE TO WOOD - THE CHANGING PANTHEON ROOF TRUSSES

THE BRONZE ROOF TRUSSES 128-1626 AD

Diagram and reconstructed image showing what the Pantheon bronze roof truss structure looked like when the Pantheon was completed
in 128 AD, an original image by atouchofrome.com

Pantheon Bronze Roof Trusses in 128 AD
Based on sketches from 1500s and 1600s (shown below)

The Pantheon's ancient bronze roof trusses were the equivalent of today's steel girders in modern buildings. In the image above, I have attempted to show how the bronze girders might have looked when new and pristine - notice the rivets that join all the large bronze beams together. The image is based on actual sketches and drawings dating from before the bronze trusses were all melted in 1625. Note the fasteners are actually rivets and not bolts, as explained in the diagram below.

Diagram comparing rivets and bolts, how they look and their attributes

Rivets compared to bolts

The first sketch below was made in 1625 by Francesco Borromini. On the left side is his original sketch, which is a bit murky. On the right is my enhanced version for more detailed and easier viewing. His original sketch showed only one complete side of the bronze roof truss - perhaps because the other side was occupied by another building that has since been dismantled. You can see where the rivets were attached as they held all the various metal sections together.

sketch of the Pantheon's bronze roof truss girders drawn by F. Borromini in the year 1625 AD

Pantheon bronze roof truss sketch by F. Borromini - 1625

The sketch below is based on another done 75 years before the image above - in the mid-1550s. It shows the bronze roof trusses at a different angle. These metal structures look surprisingly modern in design and concept.

sketch of pantheon bronze roof truss girders by an artist in the 1700s that is very clear and carefully drawn detail

Refined 1700s version of French drawing done in mid-1500s

THE MELTING OF THE PANTHEON BRONZE ROOF TRUSSES IN 1626 AD

How ironic that these magnificent and huge bronze structures, pre-dating modern steel and iron architecture by 18 centuries (see image below) and which existed for over 1,500 years, were melted down by Pope Urban VIII in 1626 to provide more cannons for the Castel Sant'Angelo fort.

The Pope justified his actions, claiming that three percent of the pillaged ancient bronze would be used in making a large canopy known as Bernini’s Baldacchino. This large structure consisted of a vast bronze canopy supported by enormous and twisted bronze columns located at the heart of St. Peter's cathedral.

There has been much conjecture about whether or not any of the ancient bronze was actually used for artistic purposes. Arguments have been put forward stating that the artist, Bernini, was very particular about the bronze mixture he used - thus, the uncertain Pantheon bronze mixture would not have been acceptable to him.

Also, Bernini already had more than enough non-Pantheon bronze available at the time and would have been quite reluctant to use any of the Pantheon bronze simply because of his great respect for the ancient and iconic structure. An example of Bernini's respect for antiquity is shown by his continual refusals when an earlier Pope, Alexander VII, wanted Bernini to alter the interior of the Pantheon in several ways (such as filling in the oculus and adding decorations to the dome coffers).

Diagram comparing ancient 1,900 year old Pantheon bronze roof trusses to modern metal roof trusses and showing that the Roman
engineering is incredibly similar to modern engineering - this is an original diagram by atouchofrome.com

Pantheon Bronze Roof Trusses Compared to Modern Metal Roof Trusses

It would thus appear that there is reason to believe that Pope Urban VIII's claims that the Pantheon bronze was used for embellishing St. Peters Cathedral were perhaps propaganda which can be seen just before you enter through the large Pantheon doors. On the left side of the entrance is a marble plaque justifying (in Latin) Pope Urban VIII's appropriation of the ancient bronze roof trusses. A part of the inscription refers to the destroyed bronze truss structure as “a useless and all but forgotten adornment.”

The citizens of Rome were outraged that their beloved Pantheon, such an important and well-preserved part of their long history, was subjected to such injury. In response, a very clever satire targetting Pope Urban VIII, whose family name was Barberini, began circulating among the people:

"Quod non fecerunt Barberi, fecerunt Barberini"
"What the barbarians did not do, the Barberini did."

However, despite the actions of Pope Urban VIII, let us remember that Pope Boniface IV saved the Pantheon by converting it into a church, and many other Popes spent a great deal of money and time in maintaining and preserving the structure. The remarkable condition of the Pantheon today and its solitary state, unattached to any other buildings, as well as the greatly improved ground level, is the direct result of centuries of Papal interventions and considerations.

ONE BRONZE RIVET IS ALL THAT REMAINS OF THE PANTHEON BRONZE ROOF TRUSSES

Rather sadly, only one large bronze rivet that joined the girders has survived. I suppose we are fortunate that anything survived. Initially, after the bronze girders were melted, many bronze rivets were still around after 1625. However, the Barberini family gave many of the bronze rivets away as souvenirs. Today, only one remains (that we are aware of), housed at the Staatliche Museen zu Berlin (Berlin Staatliche Museum).

Furthermore, I believe this Berlin museum was given the bronze rivet from a Prussian King who acquired it from a collection owned by Giovanni Pietro Bellori (1613-1696). This man was a scholar, collector, renowned biographer of great artists, and an antiquarian (person who collects or studies antiquities).

I have read that Giovanni Bellori had the only remaining Pantheon bronze rivet in his collection. And since the Staatliche Mussen zu Berlin has the only Pantheon bronze bolt in existence, it is definitely Bellori's Pantheon bronze bolt and the Berlin museum's Pantheon bronze bolt are one and the same. Edit: This has been verified by the museum and historians.

In his book Le Sacre Grotte Vaticane, Francesco Maria Torrigio (1580-1650) wrote that 152,634 kg (336,502 lbs) of bronze trusses (girders) and 3,185 kg (7,0223 lbs) of bronze rivets were removed from the Pantheon. It is sad to think how all that remains of that enormous amount of Pantheon bronze is just one rivet, pictured below with measurements:

Diagram showing an actual color photo of a huge Pantheon Bronze rivet with measurements

Ancient bronze rivet used to secure the bronze roof trusses of the Pantheon's portico entrance area

This giant rivet is 53 cm (21 inc) long and weighs over 15 kilos (30 lbs). It has also been calculated that the rivet was created using a blend of 90% copper and 10% tin that was poured into a vertical mold. This ancient rivet is quite impressive. It is definitely huge and in relatively good condition despite its tremendous age. Notice how the metal is dark within the central area but lighter in colour at both ends, indicating where the left and right sides of the girder sections made contact. The width of these lighter-coloured sections, at either end of the rivet, is 8 cm (3 in).

THE PANTHEON WOODEN ROOF TRUSSES - 1632 AD

As has been stated in the section above, the bronze roof trusses, and the whole roof structure they supported, were all destroyed in 1626 AD. And thus, a new roof above the Pantheon portico had to be designed and built using wooden roof truss supports. Fabricating new roof trusses made from metal was out of the question due to a metal shortage in 1620s Rome - this is why the bronze girders and bolts were melted in the first place.

Because of the time required to design and carry out the work, it took several years to build a new roof structure for the Pantheon's portico after the destruction of the bronze roof trusses (and the roof above) in 1626 AD. There was much debate over how the new portico roof should be designed. For example, to prevent the new wooden wood roof trusses from being seen from below, should there be a false ceiling suspended below them, or should they create a barrel vault ceiling? They decided not to make a false ceiling to hide the new wooden roof trusses.

So when were the new roof trusses and roof above completed? I have had to estimate the date as follows:

By 1632 AD, Pope Urban VIII had a marble plaque installed on the right side of the Pantheon entrance wall stating how he had rebuilt the Portico roof and added two bell towers to replace the single bell tower that had been there since 1270 AD. Assuming that plaque was placed not too long after the new portico roof was completed, I am guessing the work was done in late 1631 or early 1632 AD, a period of 5 years after the 1626 destruction of the ancient bronze roof supports. The design they finally chose is shown below, the same design we see today, almost 400 years later.

Diagram showing the complete Pantheon wooden roof truss structure from the front, this is an original diagram by atouchofrome.com

Pantheon Wooden Roof Truss infrastructure
1632 AD to Present

The overall wooden truss design is modular - each truss is divided into a central, east, and west section. This is in stark contrast to the original bronze roof trusses which, when assembled and joined with the bronze bolts, formed one coherent section, supported by the columns, stone blocks and arches below the trusses. I am assuming the wooden trusses, being almost 400 years old and still functioning well, are made of a hard and durable wood that likely is oak due to its strength and longevity. You can see all three sections in the next photo below.

HOW MANY PANTHEON WOOD ROOF TRUSSES - 3 OR 4?

At first glance, there may appear to be four trusses, but when you look closely, there are really only three free-standing and complete wooden roof trusses spanning east and west across the Pantheon portico. There does seem to be something resembling a roof truss embedded in stone, but it is inconsequential.

The image below clearly shows the phenomenon - and starting from the top of the image, you can count three obvious wood trusses and then, towards the bottom of the image, you can see the vague and rough outline of something resembling another roof truss. However, if you click on this image that shows the roof trusses from the side, you will see that the right side of the image shows there actually is nothing there.

looking up and north at all the Pantheon wooden roof trusses while standing in the entrance area

Looking up towards portico roof from entrance
Image licensed from Dreamstime.com

The diagram below shows the horizontal arrangement of the Pantheon roof truss sections.

Diagram looking down on the Pantheon wooden roof truss structure and from the front, showing 3 complete wooden roof trusses
and a possible fourth wooden roof truss

Pantheon Wood Roof Trusses from the front and looking down - showing 3 complete wood trusses and a possible fourth

Since these wooden Pantheon portico roof trusses are now 400 years old, I wonder how much longer they can be used before they must be replaced? I am sure that regular inspections are done to ensure both the safety of the people below and the integrity of the iconic structure itself. Whoever designed and built these trusses did a great job - these wooden trusses have withstood the test of time.

Kudos aside, I would much prefer to be gazing up at the original and ancient bronze roof trusses. Someday, I will travel to Berlin to gaze sadly at the last remaining piece of the bronze trusses - the only surviving Bronze roof truss bolt housed in the Staatliche Museen zu Berlin.

THE PANTHEON PORTICO FLOOR

Two photos of the Pantheon Portico (porch) floor patterns, the first image looking west to east through the columns with the
sun beaming and second image looking south at the pantheon doorway entrance and floor pattern before the door

The floor pattern of the Pantheon Portico:
- Circles and Rectangles

photo of Pantheon portico floor middle section close-up showing the black and white marblel and granite floor pattern,
looking from east to west with column bases showing

Pantheon Portico floor looking from east to west
Courtesy of Tiedyefreaks

The floor of the Pantheon Portico shares the same circle and rectangle theme found on the inside of the Pantheon. However, in contrast to the four kinds of coloured marbles and granite found on the rotunda floor, the portico floor is made up of only two kinds of stone, white marble and dark gray granite. Nevertheless, I still think it looks grand. And despite much restoration work, the portico floor's original pattern and colours remain true.

The diagram below shows the whole pattern and colour scheme of the Pantheon portico floor. You can notice how rectangles dominate - 47 versus six circles, with an overall count of 53 gray granite shapes imposed on a white marble background.

diagram showing the complete Pantheon Portico floor patterns and their true colors

The floor patterns of the Pantheon Portico floor

While there are only two sizes of circles, there are six different sizes of rectangles. Interestingly, there is no small rectangle between the second and third large circles in the very middle of the floor. In my opinion, there is a pleasant yet slightly irregular symmetry to the overall floor pattern.

Moreover, the almost "black and white" outside portico floor contrasts greatly with the inside multi-coloured and stunning rotunda floor with its reds, yellows, purple, white and gray stone slabs. This contrast is not unlike how the outside appearance of the Pantheon is rather drab compared to the inside appearance. However, I do realize that, in the past, the Pantheon outside was far more elegant when it was clad in white marble, roofed with gilded bronze tiles, and adorned with several sculptures while resting upon a high podium with a staircase.

THE GREAT PANTHEON PEDIMENT ERROR

Without a doubt, the Pantheon makes a bold statement about the time, the people, the culture, and the technical skills during the period of Roman history it was built - the early Second Century AD. The Pantheon was, and still is, an outstanding architectural achievement that has strongly influenced architecture over the centuries.

However, there is no such thing as absolute perfection, and the Pantheon is no exception. Most people looking at the Pantheon's outside surfaces will likely not notice a serious construction error. Remarkably, the Pantheon has two pediments on the front of the building, one higher than the other by 3 metres (10 feet) - see the image below.

Diagram photo showing the Pantheon higher pediment architectural error which is indicated with an arrow pointing to the error

Arrow shows outline of Pantheon's second Pediment

It is somewhat bewildering why they did not simply remove all traces of the "ghost" pediment rather than leave it there. Instead, they embellished it with modillions, making the outline more pronounced. And why is there an outline at all?

The Romans could have easily chiselled away the protruding material, afterwards covering it up with marble veneer panels. Furthermore, after the apparent high level of care and thought that went into the Pantheon's creation, it seems almost inconceivable that Emperor Hadrian and his architect would have allowed this anomaly to remain.

The higher second pediment strongly indicates that the original intention was to have a much higher portico by using taller columns. But something went wrong during the Pantheon's construction, and shorter columns had to be used.

Based on the height of the ghost pediment outline, the Romans had initially planned to use 15 metres (50 ft) high columns instead of the 12 metres (40 ft) columns from Egypt we see today. After the taller columns were quarried in Egypt and then shipped to Rome, either the ship carrying the columns sank in the Mediterranean sea, or the columns were urgently needed for some other construction project. Whatever the case, the reality is that we have a Pantheon with a Portico and pediment 3 metres (10 ft) shorter than it should have been, an architectural mystery for us to ponder.

Current Pantheon Portico roof and height compared to ancient Romans' intended Portico roof height. Current wooden roof
trusses are compared to ancient bronze roof truss girders. This is an original 'atouchofrome.com' diagram

Current Pantheon portico height compared with the ancient Romans' intended height

As you can see in the image above, a Pantheon with a higher portico looks much grander and more proportional. It really is unfortunate that something went wrong during construction, forcing the Romans to reduce the Portico's height. Just imagine yourself standing before a Pantheon with those much higher columns - what an "extra amazing" sight that would be. Nevertheless, I really like this building just the way it is, imperfections and all.

THE PANTHEON'S INFLUENCE ON ARCHITECTURE

Many architects and influential people have been inspired by the ancient Pantheon's grand structure that has survived over nineteen centuries. And history has shown that what inspires and amazes people can lead them to copy it. As a result, in the last few hundred years, many architects have used varying aspects of the Pantheon's structure in their building designs. Below, I show photos of buildings in Berlin, Paris, and Washington DC that were obviously inspired by the Pantheon's unique architecture.

photo of a Pantheon-like structure in Berlin called the Altes Museum, showing a coffered dome ceiling with a glass-covered oculus
in the centre. There are statues around the perimeter of the circular room below.

Looking in

Looking up

Altes Museum, Berlin - Room with coffered Dome & Oculus
Photos Licensed from Dreamstime.com

Like the Pantheon in Rome, the Altes Museum in Berlin has a large and circular "rotunda" room with Classical sculptures standing below a magnificent coffered dome. In addition, the "attic" second-floor section above has niches containing even more statues.

On the ground, numerous Corinthian columns stand along the perimeter. Interestingly, the marble columns appear yellowish, matching the yellow Giallo Antico columns found within the Pantheon. However, there are no observable alcoves or niches on the ground level; thus, the numerous statues stand out in the open.

Also very interesting are the ceiling coffers ornamented the way the original coffers may have been in Rome - with rosettes and bronze along the edges. But, of course, a major difference is the glass-covered oculus in the centre which is not open to the sky and weather. I suppose I cannot fault the museum because, after all, rain and snow that entered the room would have to be drained away before it caused water damage. Also, Berlin is a lot colder than Rome in winter, so you can imagine how cold this large room would get during the cold seasons.

The floor pattern - though interesting and symmetrical - differs significantly from the "circle and rectangle" geometric floor pattern of white, yellow, gray, and red tiles seen in the Pantheon. Despite some differences, this structure is still very reminiscent of the Pantheon, and I am sure the Romans would find this lovely building quite impressive.

photo of the French Pantheon in Paris interior, looking up at the central dome ceiling above tall windows and several
supporting arches below

The Pantheon in Paris, 2017
Image courtesy: Rogerio Camboim - CC BY-2.0

The photo above of the French Panthéon in the Latin Quarter of Paris is almost like a dream to me. We see a high and beautiful coffered Pantheon-styled dome atop a rotunda composed of white Corinthian columns interspaced by tall windows that fill the interior with bright light. The rotunda seems to be almost floating above the rest of the structure.

This domed structure, supported by a series of huge arches rising from the floor below, is very reminiscent of the Hagia Sofia building in Istanbul, Turkey (formerly the city of Constantinople, capital of the Roman Eastern Empire for over 1,000 years). And the large arches and elaborate wall decorations are very Roman in style and execution.

In addition, the architecture is very Corinthian, as shown by the elegant Cornice running along the walls between the arches and the circular Cornice below the dome and rotunda. There are also hints of the late Baroque style in the wall paintings. This is a magnificent building and great architectural accomplishment of the late 1700s.

It is fascinating to see how, over the centuries, people have borrowed architectural concepts from the Pantheon and then imaginatively expanded the concept in new directions.

photo of the Jefferson Memorial in Washonton DC at night showing the front columned portico and dome behind reflecting on a wide
expanse of water

The Jefferson Memorial in Washington DC, 2018
Image courtesy: John Brighenti - CC BY-2.0

And here, far from Rome, in the Capital of the U.S.A., we find a near-Pantheon-clone. Just like the Pantheon, we see a wide portico, eight columns wide (octastyle), with a typical Roman pediment above. And behind, we behold a circular building crowned with a large dome. This building is absolutely 100% a structure that was inspired by the Pantheon in Rome.

A major difference is how this building uses the Ionic Order instead of the Pantheon's Corinthian Order. Another difference is the Jefferson Memorial's wide and steep staircase that creates a dramatic entrance to the structure. While the Pantheon actually does have a staircase, it has been buried for many centuries; also, its staircase was only about five steps high.

I can confirm that the inside surface of the dome is indeed coffered. However, this dome does not have an opening in its centre (oculus) to the outside. Nevertheless, the outside world still enters the circular room below through the sides which are composed of open gaps in the walls. These gaps contain several columns, creating a remarkable effect, as shown in the remarkable photo below. Below a Pantheon-styled dome, a large statue of Thomas Jefferson occupies the interior space.

photo of the Jefferson Memorial interior showing dome and much of the structure

Jefferson Memorial Interior in 2012
Image courtesy: Zach Frailey - CC BY NC-ND 2.0

This is a really stunning building. The effect outside, when standing in front of the wide staircase and looking up, is also very impressive. This building represents neoclassical architecture at its very best. There are many other examples of buildings inspired by the Pantheon, especially in the USA, where examples are found in Universities, memorials, and Government buildings.

THE PANTHEON REAR SECTION

Reconstructed image showing the Pantheon from the rear in 320 AD, showcasing the Basilica of Neptune that was located behind
the Pantheon and other surrounding buildings in the vicinity of the Pantheon in 320 AD

image showing the Pantheon from the rear in year 320 AD with surrounding buildings labelled

Rear view of Pantheon in 320 AD
Move Cursor or Finger Over Image to See Labels
Image of Plastico di Roma Imperiale

Every image and video of the Pantheon shows us a great front view of the structure. However, when seen from behind, one beholds a very ancient and square building attached to the rear of the Pantheon. What is this building? What is its purpose?

The image above shows us the Campus Martius area of Rome in 320 AD, where the Pantheon has a large basilica attached directly to its rear wall. And behind that basilica, bottom right corner, is the Baths of Agrippa, with the Baths of Nero in the bottom left corner. Move the cursor or tap the image to show labels on all the buildings.

Photo of structures attached to Pantheon rear as seen from the south east

View of Pantheon rear in 2015

This view of the Pantheon rear in 2020 shows us what remains of the Basilica of Neptune, built in 25 BC by Marcus Agrippa. He built this basilica to commemorate his naval victories, most notably the battle of Actium, where he defeated the naval forces of Marc Antony and Cleopatra in 31 BC.

In 80 AD, the fire that destroyed the second Pantheon also damaged the Basilica of Neptune, which Emperor Hadrian then rebuilt. On the far left of the structure, one can see some white marble entablature sections that have survived. These marble decorations give us a glimpse of how those brick walls looked long ago. The image below shows those marble sections in greater detail.

photo closeup of pantheon rear wall white marble remains from the Basilica of Neptune showing symbols of Neptune such as
tridents, whales and seashells

Close-up of Basilica of Neptune's surviving marble entablature
Image courtesy: Aaron Vowels - CC BY 2.0

The marble details show the symbols of the Roman god Neptune - tridents, shells, and whales. And we are looking at the inside wall of the Basilica of Neptune, which would have been much wider and deeper than the small square structure adjoining the rear of the Pantheon today.

This building houses buttresses that bolster the Pantheon's south side. This was necessary because, shortly after the Romans poured the current Pantheon's foundation, they noticed the foundation was cracking and sinking along the southern section (opposite the North entrance). To correct the problem, the Romans built an even wider foundation and created buttresses to reinforce the south side.

Notice the ancient Roman windows along the top (above the white marble sections), a common feature of Roman baths and basilicas for lighting the interior. The Romans developed window glass as well as glass vessels and ornaments. These surviving white marble fragments suggest how differently the walls of Roman buildings would have appeared in the past. Today, we see primarily Roman structures made of brownish brick because the marble panels and decorations that covered the brick understructures have been removed or have fallen. The Pantheon's outside walls were covered with a combination of primarily white stucco and a limited amount of Pentelic marble panels, nearly all of which have vanished over the ages.

Photo of Pantheon from above looking from the eastern side showing the narrow street and amount of space behind the Pantheon in
the year 2020 AD

"Via della Palombella" street behind the Pantheon
Thank you to Google Earth for image

The image above shows why nearly all views of the rear of the Pantheon are angled views - there just is not enough space back there to afford a good camera view of the whole rear structure. The amount of clearance between the two buildings is not very wide, as seen in the photo. The street behind the Pantheon is the Via della Palombella which actually houses a few businesses.

Photo of the Pantheon rear section taken in the year 1900 while standing on the ground and looking north west -
photo is black and white

Pantheon rear in the year 1900

LIST OF CHANGES TO THE PANTHEON SINCE 128 AD

The Pantheon is an exceptionally well-preserved Roman building, despite having an outside that was stripped down to bare concrete and brick. What makes the Pantheon the best preserved Roman structure is its stunning inside that has been well-maintained by using both new materials and resurfaced ancient materials.

Of course, certain aspects of the Pantheon's original structure have changed. Nevertheless, the Pantheon is still a marvellous visual architectural experience resembling closely what the ancient Romans also experienced.

In the 21st century, the Pantheon we see today is the result of many centuries of restorations, cleanings, digging, and replacing. Below is a list of these activities:

•	All the original statues were removed;
•	The bronze roof tiles were all removed;
•	The Portico tympanum bronze eagle and other decorations were removed;
•	Lead plating was installed over the dome;
•	99% of the outside wall marble was pillaged;
•	The dome ceiling's original dark blue colour with bronze accents in each coffer was covered with gray plaster;
•	Several front columns were replaced;
•	The interior upper wall surface (Attic) was replaced;
•	Several of the seven alcoves that housed statues were rebuilt;
•	Statues of Saints, and tombs for Monarchs and a painter, were added;
•	Imperial Porphyry stone columns replaced by cheaper granite columns;
•	The Portico's bronze roof girders were removed and melted;
•	Portico Bronze Suspended ceiling below Bronze Girders removed and melted;
•	A single Bell tower was added to the Pantheon roof and later demolished. It was replaced with two new bell towers, which also were demolished in the late 1800s.
•	2/3 of the Pantheon floor was either resurfaced and/or replaced;
•	Bronze letters added to replace the ones missing on the front of the Pantheon;
•	The original Pantheon doors were cleaned and cosmetically altered into the form seen today;
•	Ground level of the area in front of the Pantheon lowered to Portico floor level. Nevertheless, over 90% of the Pantheon podium and staircase are still buried.

Considering how few Roman buildings are in as good a condition as the Pantheon, we are indeed fortunate today to have the opportunity to glimpse the splendour and genius of Roman architecture in the way that the ancient Romans did. The only other Roman building that nearly matches the Pantheon is the Maison Carrée Roman Temple in Nimes, France.

Nearly always, all we see are partial Roman ruins that require much imagination to visualize and appreciate what once was -- thankfully, the Pantheon is one of the great exceptions to that sad reality. Are there other significant exceptions like the Pantheon? I think the Maison Carree in Nimes, France and the Curia Julia in Rome are also exceptionally well-preserved, though a little bare on the inside.

THE TIBER RIVER AND PANTHEON FLOODING

Since ancient times, the inhabitants of Rome have been contending with flooding caused by the Tiber river which runs through the centre of their city. By building walls, dredging the river, clearing drains, and maintaining good sewer systems, the ancient people of Rome developed effective ways to help reduce both the number and intensity of floods. However, after the Roman Empire collapsed, that system of flood prevention fell into disrepair, sewers became clogged, and floods again became frequent.

Two or three times each century, the Pantheon has had to contend with floods and all the consequential damage caused by water, humidity and mould. It is thus not surprising that sections of the Pantheon floors, both inside the Rotunda and outside in the Portico, have been replaced. After the last flood of 1937, the City of Rome took strong measures to prevent further flooding. So far, the measures they took have been very effective, and Rome has been free from floods for over 80 years.

Pantheon flooded by Tiber river in December 1870

The image above shows the extent of flooding around the Pantheon in 1870. It looks like the whole neighbourhood was flooded. That poor woman on the balcony must be distressed at the sight of so much flooding. Undoubtedly, the Pantheon's floors were covered with water, which must have caused some damage. In the photo below, taken 30 years later, we see another flood in December of 1900. Today, in some areas adjacent to the Tiber river, 15 metres (49 feet) high embankment walls have been built along the sides of the Tiber river to tame it and protect the people and architectural treasures of Rome.

photo of flooded Pantheon in December 1900

Pantheon flooded by Tiber river from December 1 to 3 1900.

The Pantheon has been flooded many times during its 1,900-year existence. For example, between 414 BC/BCE and 398 AD, there were 33 recorded floods. In addition, historical records show that the Tiber river has flooded the city approximately every 50 to 100 years, sometimes even three times per century.

After the fall of the Western Roman Empire in 476 AD, there have been floods in 1230, 1277, 1379, 1476, 1530, 1557, 1589, 1598, 1606, and 1805 - these are just a sampling of years and not a complete list. Most flooding occurs from November to February and more commonly during December.

Pantheon flooded by Tiber river in November 1937.

And as shown in the photographs on this page, there were floods in 1870, 1900 and 1937, which was the year of the last flood. Fortunately, the City of Rome now seems to have the flooding situation under control as there has not been a flood in over eighty years. Interestingly, it was a revival of the ancient Roman techniques of dredging the river, clearing the drains and sewers, and building protective embankment walls along the Tiber river that has contributed significantly to preventing floods.

During the Dark Ages, after the fall of Rome in 476 AD, and throughout the Middle Ages and beyond, the people of Rome allowed the rivers, drains and sewers to fill up with refuse, debris, and sediments. A Tiber river less deep and clogged up led to a river much more prone to overflowing its banks. Furthermore, clogged drains and sewers led to the river becoming less able to drain effectively. Without a doubt, the key to taming the Tiber lay in reviving the techniques practiced by the ancient Romans. I wish the City of Rome continued success.

This ends the discussion of the Pantheon. I hope you have come to a greater understanding of this iconic structure and appreciate its unique and enduring construction. The quote below summarizes well the sentiments of many people towards the Pantheon:

“By every measure of success of a building—from an architectural, from an artistic, and from an engineering standpoint—I would argue that the Pantheon is the greatest that was ever built ... There’s no greater definition of success for a building than it’s been standing for 20 centuries.”

John Ochsendorf, Prof. Engineering & Architecture, MIT