A striking 2000-year-old temple, now a church, the Pantheon is Rome's best-preserved ancient monument and one of the most influential buildings in the history of architecture.
Its gray, pockmarked exterior might look its age, but it remains a unique and exhilarating experience to pass through the Pantheon's vast, bronze doors and gaze up at the largest unreinforced concrete dome ever built.
Historical Development
In its current form, the Pantheon dates to around 125 CE. The original temple was built by Marcus Agrippa in 27 BCE as part of an urban development program launched by Emperor Augustus. However, that temple burnt down in 80 CE, and although it was rebuilt by Domitian, it was struck by lightning and destroyed for a second time in 110 CE. Emperor Hadrian had it reconstructed in 125 CE, and this is the version you see today.
It’s thought the original temple was dedicated to the classical gods – hence the name Pantheon, a derivation of the Greek words pan (all) and theos (god) – but its exact religious function remains something of a mystery. In 608, it was consecrated as a Christian church and took the name by which it is still officially known, Basilica di Santa Maria ad Martyres. During the Renaissance, the building was much admired – Brunelleschi used it as inspiration for his cupola in Florence, and Michelangelo studied it before designing the St Peter's Basilica dome – and it became an important burial chamber. Artists Raphael, Annibale Carracci and Baldassare Peruzzi are buried here, alongside Kings Vittorio Emanuele II and Umberto I.
The Exterior
Originally, the Pantheon was on a raised podium facing a rectangular porticoed piazza. Today, the dark-gray exterior faces the busy, cafe-lined Piazza della Rotonda. And while its facade is somewhat worse for wear, it's still a formidable sight. The monumental entrance portico has 16 Corinthian columns, each 11.8m high and made from a single shaft of Egyptian granite, supporting a triangular pediment.
Behind the columns, two 20-tonne bronze doors give onto the central rotunda. Whether these vast doors, which can be opened by a single person, are the originals or whether they’re 16th-century copies remains the subject of lively debate. One thing historians do agree upon is the fact that when the columns arrived from eastern Egypt, having been transported over land, river and sea on wooden sleds and barges, they were found to be too short. Undeterred, the engineers modified their plans and continued with the construction.
Little remains of the original ancient decor, although rivets and holes in the brickwork indicate where marble-veneer panels were once placed. Bronze also featured heavily in the original temple, but over the centuries, much of this has been stripped off. Notoriously, the 17th-century Barberini Pope Urban VIII had the portico’s bronze beams melted down to make 80 cannons for Castel Sant'Angelo and to provide Bernini with bronze for his baldachin at St Peter's Basilica. This act of architectural recycling gave rise to the saying, still in use today: 'What the barbarians didn't do, the Barberini did for them'.
The Interior
Although impressive from outside, it’s only when you get inside that you can truly appreciate the Pantheon's breathtaking size. With light streaming in through the oculus (the 8.7m-diameter hole in the center of the dome), the cylindrical marble-clad interior seems vast, an effect that was deliberately designed to cut worshipers down to size before the gods.
Opposite the entrance is the church’s main altar, over which hangs a 7th-century icon of the Madonna col Bambino (Madonna and Child). To the left (as you look in from the entrance) is the tomb of Raphael, marked by Lorenzetto’s 1520 sculpture of the Madonna del Sasso (Madonna of the Rock). Neighboring it are the tombs of King Umberto I and Margherita of Savoy (after whom pizza margherita is named). Over on the opposite side of the rotunda is the tomb of King Vittorio Emanuele II, Umberto’s father and the first king of post-unification Italy.
Before leaving, make sure to look down as well as up – the elegant polychrome marble that covers the floor and most of the internal walls is original.
The Dome
Crowning everything, the Pantheon’s dome is considered the Romans’ greatest architectural achievement. It was the largest cupola in the world until the 15th century, and it is still the largest unreinforced concrete dome in existence. Its harmonious appearance is due to a precisely calibrated symmetry – its diameter is equal to the building’s interior height of 43.4m.
At its center, the oculus, which symbolically connected the temple with the gods, plays a vital structural role by absorbing and redistributing the dome's huge tensile forces. It also, of course, lets rain into the building. But thanks to an updraft that forms in the interior, raindrops are broken down into tiny droplets that are almost invisible to the naked eye. This "chimney effect" transforms water into a mist, which disappears shortly after it touches the convex floor, which is fitted with 22 almost-invisible drainage holes.
Radiating out from the oculus are five rows of 28 coffers (indented panels). These were originally ornamented, but more importantly, served to reduce the cupola's immense weight.
