The Pantheon: The Secrets & History Of The Roman Empire’s Symbol

The Pantheon is one of the best-preserved monuments from ancient Rome. Built at the height of the Roman Empire, Agrippa’s Pantheon was used to promote the emperor’s power and legitimacy. Even today, the building stands as a lasting reminder of imperial glory. It is also one of the most influential historical edifices since its design has been the subject of imitations all over the world. An inspiration to countless generations of artists, and one of the most favored tourist spots in the world, the Pantheon is imprinted in our collective memory. Yet, the “sphinx of the Campus Martius,” as the monument is sometimes described, holds many secrets.

The inscription on the frieze commemorates the person who built the Pantheon around 25 BCE. Marcus Vipsanius Agrippa was the best friend and son-in-law of the first Roman emperor, Augustus. Agrippa was a man of many talents, one of them being an architect. The Pantheon was built to honor Augustus’ military victory at the battle of Actium in 31 BCE, the defining moment in the establishment of the Roman Empire. Traditionally, Agrippa’s Pantheon was thought to be small and conventional – a Greek-style temple, rectangular in plan. But archeological studies suggest that the original building resembled the current structure.

Ironically, the building that nowadays stands in the historical center of Rome is not the one built by Agrippa. After a fire destroyed much of the original construction around 80 CE, emperor Domitian restored the Pantheon to an unknown extent. Domitian’s building burned down again in 110 CE. It was believed that the Pantheon got its iconic form during the reign of emperor Hadrian. Recent archaeological findings, however, question that theory. The bricks used in the construction date back to the 110s, to the reign of Hadrian’s predecessor Trajan.

Instead of a great triumph of Hadrianic design, the Pantheon should be seen as the final architectural glory of Trajan, the emperor who brought the Roman empire to its greatest territorial extent. Designed and rebuilt around 114 CE, with some preparatory work perhaps starting immediately after the fire of 110, it was finalized and dedicated by emperor Hadrian in 126 CE. Neither emperor, however, denied the importance of Agrippa’s original. The inscription on the front of the building proudly names its original designer:

M·AGRIPPA·L·F·COS·TERTIVM·FECIT – “Marcus Agrippa, son of Lucius, built this when he was consul for the third time.”

Traditionally, it was believed that the Pantheon was constructed to be a temple to all gods. Its name is derived from the Greek words pan, meaning “all,” and theos meaning “gods.” Several scholars have recently suggested that instead of a traditional temple to the gods, the building was a dynastic sanctuary, linked to emperor Augustus and his family.

According to Cassius Dio, our primary source, the original dedication of the edifice was to Julius Caesar, the progenitor of the Julio-Claudian dynasty. Caesar was also the first Roman ruler deified by the Senate, with Augustus and other Roman emperors following in his footsteps.

To this, we can add the sacred associations of the site itself, since the Pantheon was built on the Campus Martius, a place believed by the Romans to be the location of the apotheosis (raising to the heavens) of Romulus, Rome’s mythic founder.

Further, the Pantheon was aligned on an axis with the Mausoleum of Augustus, completed just a few years before the Pantheon. Agrippa’s building, thus, suggests an alliance between the gods and the rulers of Rome, at the moment when a new imperial cult was taking shape.

Augustus’ successors took this sacred connection to the next level. Emperor Hadrian, who finalized the reconstruction of the Pantheon, even held a court in the building. By his time, the direct line of sight between the Pantheon and Augustus’ Mausoleum had been blocked, but the building retained its link to imperial legitimacy. By keeping (or recreating) Agrippa’s inscription, Hadrian subtly associated himself with the first emperor, suggesting that he was part of the natural succession of (deified) emperors. It is perhaps unsurprising that we find Hadrian’s mausoleum (Castel Sant’Angelo) in the vicinity of both monuments.

Writing in the fourth century CE, historian Ammianus Marcellinus mentions statues of the Roman emperors occupying the rotunda’s alcoves. Whatever its original purpose, the Pantheon became primarily associated with the power of the emperors and their divine authority. And as we shall see, the Pantheon was also an arena in which the emperor could remind Rome’s populace of the extent of the empire, and his personal control of it.

The Empire In Miniature

In the Roman period, the approach to the Pantheon was framed and directed by the long walls of a courtyard or a forecourt in front of the building, and a set of stairs, now submerged under the square. Directly in front of the portico, there was an arch called the Arch of Piety. It was a memorial arch, possibly used for processions. Once the arch was passed, a visitor would see a building clad in white marble imported from around the empire.

Even today, the Pantheon’s portico contains tall, monolithic Corinthian columns made of famed Egyptian granite. Besides its quality, the granite had a symbolic value, representing the southernmost frontier of the vast empire. Further, the use of Egyptian granite was monopolized by the emperor, thus symbolizing his immense power.

The symbolism does not stop here. The columns had bases of fine-grained Pentelic white marble which came from Greece, while yellow Numidian marble from Tunisia was used for the steps. The empire-in-miniature fully reveals itself inside the edifice. Much of the interior decoration has been restored, but traces remain of Numidian yellow, Phrygian purple, and Lucullan black marble (both coming from Asia Minor). The roundels are made of red Egyptian porphyry, one of the world’s rarest stones, which was used exclusively by the emperor and his family.

Shipping stone from a remote province like Egypt was an expensive endeavor and it could be done only by someone extremely wealthy and powerful, like an emperor. Trajan and Hadrian choose to import marble, porphyry, and other expensive building materials from around the empire to Rome as a display of power to the people of Rome who would see or visit the building on a regular basis.

Beneath the exotic opulence lies the triumph of Roman engineering. The walls are made of brick-faced concrete (opus testaceum), an innovation widely used in Rome’s major buildings and infrastructure, such as aqueducts. They have been lightened with relieving arches and vaults fixed by wedges. Concrete allowed for spaces to be carved out of the walls, like the alcoves, which contained statues of gods and emperors.

But the true brilliance of the Pantheon reveals itself when one looks up. The largest dome in the Roman world covers the drum, with natural light spilling onto the walls and alcoves from the nine-meter-wide (30 foot) oculus at the dome’s center. The coffered ceiling (sunken panels) and oculus serve not only as decoration, but are also practical features, lessening the weight load of the dome. The specific concrete used for the dome was exceptionally light. A combination of limestone and volcanic ash used in the mortar helped to form the crystals that prevented the spread of microscopic cracks, and eventually, the dome’s collapse. At 43.3 (142 feet) meters in diameter, the Pantheon’s dome is still the largest dome in the world that does not use reinforced concrete.

Remarkably, the height of the oculus and the diameter of the dome is exactly the same, 43.3 meters. This means that a giant sphere with a diameter of 43.3 meters could fit inside the interior space. Besides its practical use, the oculus had another purpose. The round opening could serve as a sundial. The sunbeam streaming through the oculus traced an ever-changing daily path across the wall and floor of the rotunda. Perhaps, then, the sunbeam marked solar and lunar events, or simply time. The idea fits nicely with Dio’s depiction of the dome as the canopy of the heavens and, by extension, of the rotunda itself as a microcosm of the Roman world, with the emperor presiding over it, ensuring the right order of the world.

Transformation Into A Church

Little is known about what happened to the building after Christianity became the official religion of the Empire. It is very possible that from the early fourth to the early seventh century, the Pantheon, like most of the public buildings of Rome, fell into disrepair. The forecourt and all adjacent buildings were demolished or replaced. The only reliable information is a report from the Liber Pontificalis, which tells us that the Byzantine emperor Phocas gifted the Pantheon to Pope Boniface IV in 609. In 613, the ancient Roman building was converted into the church of the ever-virgin Holy Mary and all the martyrs.

The consecration of the Pantheon assured its survival up to the present day. Nonetheless, it did suffer some losses. Over the centuries, the golden roof was replaced with one of lead, the marble façade was removed, while the bronze coating was stripped from its ceiling. The interior columns made of porphyry were replaced by a granite version. The most striking change happened in the early 17th century when Pope Urban VIII commissioned a pair of bell towers to be added above the portico. These towers – mocked by the people as “the ass’s ears” – were finally demolished in 1883.

Following its conversion into a Christian church, the Pantheon became a burial place. In the seventh century, the holy relics of the martyrs were removed from the catacombs and transferred to the newly-founded church.

During the Renaissance, the Pantheon became a final resting place for prominent artists, including the painter Raphael, the composer Arcangelo Corelli, and the architect Baldassare Peruzzi. Two kings of Italy, Vittorio Emanuele II, and Umberto I, along with Umberto’s wife Margherita of Savoy also have their final resting place inside the Pantheon.

As one of the best-preserved ancient Roman monuments, it is not surprising that the Pantheon became a model that left a lasting impression on Western architecture. The famous Renaissance architect, Andrea Palladio adapted the Pantheon design for the Villa Almerico-Capra near Vicenza. But it was Filippo Brunelleschi who decided to emulate the Pantheon on a grand scale. The ancient Roman building was a model for the dome of the Florence Cathedral, completed in 1436. The Brunelleschi cupola surpassed the Pantheon’s dome by a large margin, but it could not surpass the brilliance of the original. He had to abandon the original plan to include the oculus, and used bricks instead of concrete since the original formula had been forgotten.

Michelangelo too was awed by the Pantheon, reportedly saying that it was designed by angels, not a man. The ancient Roman landmark was used as an inspiration for Michelangelo’s design of the dome of St. Peter’s Cathedral in Rome, which would be completed after his death. The aptly named Panthéon in Paris, originally built as a church, and later repurposed as a secular mausoleum, was also inspired by the Roman prototype.

The influence of the unique design was not limited to Europe. The American founding fathers were also fascinated by the Pantheon. Thomas Jefferson modeled both Monticello – his home near Charlottesville, Virginia – as well as “The Rotunda” at the University of Virginia, after the famous Roman building. The Jefferson Memorial in Washington, DC, completed in 1943, is another famous Pantheon-like structure. Washington is also the home to two more famous buildings that follow the Roman model: the U.S. Capitol and the National Art Gallery. The dome-and-portico design can be found in American state capitals, and in many other places around the world. And it all began with Agrippa.

The Pantheon: Afterlife

The Pantheon, with its central position in the city of Rome, was a prominent symbol of imperial power. Built by Agrippa to commemorate the triumph of the first emperor, Augustus, the Pantheon redefined public spaces, playing an important role in promoting the imperial cult, solidifying the emperor’s legitimacy, and linking the later dynasties to the first emperor. After its reconstruction by Trajan and Hadrian, the Pantheon became a showcase of imperial power. The extensive use of exotic and expensive decorative stones reflected the wealth and influence of its builder, the emperor himself.

The Pantheon was also a triumph of Roman engineering and ingenuity. Its architects employed the techniques that nowadays would be difficult to emulate, creating an architectural marvel. Almost two millennia after its construction, its celebrated dome remains the largest in the world to be built from unreinforced concrete. Despite its transformation into a church and changes that followed, the Pantheon’s design remains largely the same as it was under Emperor Hadrian. This unique design inspired countless artists and architects all around the world, with mini-Pantheons emerging not only in Europe but also across the Atlantic.

Between its rich history, its architectural legacy, and its endurance, the Pantheon is a lasting testament to the glories of its builders. A monument as eternal as the city in which it stands. Next time when you visit Rome and find yourself in front of this truly majestic building, take a good look. Read the name of its original builder, Marcus Agrippa. Look at the exotic stone, a witness to Roman imperial might at its greatest extent. When you finally enter the cavernous space, look around and above, and admire the triumph of human ingenuity. And when the sunlight falls on the Pantheon’s walls or the floor, imagine how the ancient Romans felt, in the presence of their rulers and their gods. No wonder that for centuries, many tried to emulate this feeling.