The Pantheon

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Podcast Transcript

Located in the heart of Rome is one of the oldest standing buildings in the world. Unlike other ancient structures, it isn’t a ruin. For almost 2,000 years, it has been in continuous use.

When it was built, it was an unrivaled architectural masterpiece. Today, it remains the largest building of its type, having never been surpassed in all of history.  

Learn more about the Roman Pantheon, how it was built, and what makes it unique on this episode of Everything Everywhere Daily.

The Pantheon holds the distinction of being the building from the ancient world, which has survived into the modern day in the best condition. 

Despite showing its age, especially on the exterior, it isn’t fundamentally different from what it looked like about 1900 years ago. It has been kept in remarkable condition, and it still brings in millions of visitors annually. 

Basically, it isn’t a ruin. It isn’t crumbling and doesn’t requires us to envision what it might have looked like when it was built. 

The story of the Pantheon begins with someone who was the subject of a previous episode: Marcus Agrippa. 

As I noted previously, Agrippa was arguably the best number-two guy in history. He was the best friend of Emperor Augustus since they attended school together, and it was Agrippa who Augustus turned to when he needed to get something done. 

Whether it was military or civil, Agrippa could be counted on to make sure that things happened and that they were seen through to completion. 

After the Battle of Actium, where Augustus and Agrippa defeated Marc Antony, it effectually ended the civil war and the period of political instability which had plagued Rome for fifty years, starting with the war of Marius and Sulla. 

In this new era of peace, Augustus set to rebuilding much of Rome, which at the time, wasn’t the city of monumental structures it later became. It was dingy and sprawling, and Augusut didn’t think it befitting the capital of the world’s largest empire. 

Agrippa was tasked with overseeing much of the construction in the city.

As part of the construction, outside the city limits, Agrippa oversaw the building of several structures on property he owned in the Campus Martius. The Campus Martius was land between the Tiber River and the Pomerium, which was the ritual boundary of the city, which I covered in a previous episode.

The buildings he constructed here were a complex of three structures: the Baths of Agrippa, the Basilica of Neptune, and the Pantheon. 

The word Pantheon literally means “all the gods,” and the name would imply that this was a temple for all of the gods. However, there is good reason to believe that this wasn’t the case and that it wasn’t the original name or purpose of the building.

Cassius Dio, a Roman Senator who lived almost 200 years after Agrippa, hinted that “pantheon” might just have been a nickname for the building. The idea of a building for all the gods was something that didn’t exist anywhere else in the Roman world. 

Moreover, there is evidence to suggest that the Pantheon wasn’t even a public temple. It might have been built for the personal use of Agrippa, which would explain why there was such confusion about the original name and purpose of the building. 

Regardless, the structure built by Agrippa sometime around 25 BC burned down in the year 80 when a major fire swept through Rome. This was a different fire than the great fire during the reign of Nero.

The structure was immediately rebuilt by the Emperor Domitian, and that new building burned down just 30 years later. 

During the reign of Trajan, the building was rebuilt yet again, and this is the version of the building that stands today. 

The construction of the current building is often credited to Emperor Hadrian. However, it is now believed that construction started during the reign of Trajan, perhaps during the late reign of Trajan around the year 113.

If this is true, then the architect of the building was probably Trajan’s principal architect Apollodorus of Damascus. This would make a lot of sense as Apollodorus was the greatest architect of his era and was well-known for his use of domes. 

Construction, dated by the use of brick stamps, was most probably completed and mostly took place under the reign of Emperor Hadrian. This is why Hadrian is usually credited with the construction of the current building, and this is not untrue, but it is also probably not wholly true. 

Hadrian was one of the least egotistical emperors when it came to buildings. Most emperors slapped their names on everything built during their reign. 

In the case of the Pantheon, Hadrian’s name isn’t on the building. Rather, in the front of the building, located prominently on the facade, is an inscription that reads as follows:


Even if you know Latin, inscriptions such as this can be tricky to read because they use lots of abbreviations. 

Here is what it means, with the abbreviations translated:

M·AGRIPPA obviously means Marcus Agrippa.

L·F means Lucii Filius, which means son of Lucius

COS·TERTIVM has a bit of controversy behind it. It could mean “third consulship” or “three-time consul.” The distinction is subtle, but it would indicate if the inscription was there when Agrippa was alive or if it was written about him after he was dead. 

The only other references using COS·TERTIVM with regards to Agrippa were on coins minted after he was dead, meaning this may have been written about Agrippa, not by Agrippa.

Finally, FECIT simply means “he made” or “was made by.”

So, this inscription was most probably to honor Agrippa, who was still thought of highly in Rome and was the person who commissioned the original building. 

The inscription has led to centuries of confusion as to when the current building was made and who built it.

As for the building itself, the front of the structure has a traditional temple facade. It is rectangular, with several columns and a triangular pediment above the columns.  The eight front Corinthian columns and eight rear columns form the portico. 

This is not the noteworthy part of the building. What makes this building special is what is behind it. 

The rest of the structure is a giant unreinforced concrete dome.  The diameter of the dome is approximately 43 meters or 142 feet, and the height of the dome is exactly the same. 

This means that the entire dome approximates the shape of a giant sphere. 

There was no other building like this ever built in Rome or in the entire ancient world that we know of. No other ruins have been found, and no references to such a building were made. 

Previously, I did an episode about Roman concrete and how it had incredible properties which allowed projects built with it to have survived so long. The Pantheon is probably the best and most prominent example of the strength of Roman concrete. 

I mentioned that the Pantheon was the largest unreinforced concrete dome. Modern concrete used in roads and bridges is reinforced with metal known as rebar. Rebar does improve the tensile strength of concrete. However, it comes at a cost. Reinforced concrete deteriorates much faster than unreinforced concrete. 

This is why so many modern bridges and buildings made out of reinforced concrete are already falling apart. However, that is for another episode.

At the top of the dome is an opening known as an oculus. The oculus allows sunlight to enter the dome, and it also allows rain to enter the dome. I’ve visited the Pantheon on days when it rained, and they had to cordon off the central part of the floor inside because it gets wet.

The Pantheon dome really is a wonder of ancient engineering and is evidenced by the fact that it remains the largest such dome in the world today. 

The construction of the dome is only one part of the legend of the Pantheon. The other part has to do with the fact that it is still standing and is in relatively good condition. 

As with many buildings, it did fall into a state of disrepair after a while.  In 202, the building was renovated by the emperor Septimius Severus and his son Caracalla, and there is an inscription inside that documents this.

The thing which changed the trajectory of the building occurred in 609, when the Byzantine emperor Phocas, who still controlled the city of Rome at the time, gave the building to Pope Boniface IV. 

This was the first time that a pagan Roman building was converted to use as a Christian church. The medieval historian John the Deacon noted, 

“Another Pope, Boniface, asked the same [Emperor Phocas] to order that in the old temple called the Pantheon, after the pagan filth was removed, a church should be made, to the holy virgin Mary and all the martyrs, so that the commemoration of the saints would take place henceforth where not gods but demons were formerly worshipped.”

The building was renamed the Church of St. Mary and the Martyrs. 

Relics from Christian saints were taken from the catacombs around Rome and brought to the newly consecrated church. 

Its conversion to a church is what protected the building in the years since. Unlike other Roman buildings, the Pantheon was in continuous use, and thus there was always an incentive to keep the building in a condition where it could be occupied. 

That being said, some parts of the structure are gone. Much of the exterior marble was taken to be reused in other projects, which was the case for most of the ancient structures in the city. However, much of the interior marble has remained. 

There was a bronze roof on the portico which was removed by Pope Urban VIII in the 17th century. He also added two bell towers to the buildings, which became known as the “the ass’s ears,” which were taken down in the 19th century. 

The family name of Urban VIII was Barberini, and that led to a joke in Rome which was in Latin: ‘quod non fecerunt barbari, fecerunt Barberini.’  

It translates to “what the barbarians didn’t do, the Barberini did.”

The Renaissance saw a revival of all things Roman, and the Pantheon took on a new life as an inspiration to artists and architects. Most design elements of the neo-classical style came from the facade and portico of the Pantheon, which was the best example that could actually be studied. 

Several notable artists from the period were buried in the Pantheon, including Raphael and Annibale Carracci.  Two modern kings of Italy, Vittorio Emanuele II, and Umberto I, are both buried there as well. 

Today the building is still used as a church, and services are held every Sunday. Visitors are asked to dress appropriately for visiting a church. Despite being used as a church, the building is owned by the Italian Ministry of Cultural Heritage and Activities and Tourism. 

One interesting thing I’ll close on has to do with the buildings around the Pantheon. Over time, cities were built on the ruins of what came before it. It was cheaper and easier to just build on top than it was to remove rubble.

The Pantheon, however, has never moved. It is where it was 1900 years ago and remains on the same original level. If you look at an image of the Pantheon, you will see the roads ramp upward on either side of the building. 

This isn’t because the Pantheon was built on the side of a small hill. It is because the rest of the city moved up over time. 

The Pantheon is rightly considered one of the greatest architectural wonders in the world, and for good reason. The Romans managed to create a concrete dome so large that it has never been surpassed in almost 2000 years. A design that has proven so strong and durable that it can still be enjoyed by people today.