If you only have time for one ancient building in Rome, this is it. The Pantheon Rome guide below is my attempt to explain why a 1,900-year-old temple still makes architects go quiet and first-time visitors stand in the middle of the floor staring at the ceiling. Pantheon history is, for my money, the single best story in this city. It's about ambition, engineering that still shouldn't work, and a building that refused to die.
How the Pantheon was built
The Pantheon you walk into today was built by Hadrian around 125 AD, on the bones of two earlier temples that both burned down. The inscription across the portico, "M. AGRIPPA L.F. COS. TERTIUM FECIT," credits Marcus Agrippa, who put up the original in 27 BC. Archaeology says Hadrian rebuilt the whole thing. He left Agrippa's name up anyway, which is either humility or a flex, depending on your reading.
The dome is the reason any of us are here. 43.3 metres across. It was the world's largest unreinforced concrete dome for over 1,300 years, and it still holds the record. No rebar. No steel. Just Roman concrete, poured with brains: heavy travertine and tufa near the base, lighter volcanic pumice up by the oculus. The inside is coffered with five rings of 28 recessed panels, which takes weight out of the dome and also just looks incredible. The walls at the bottom are more than 6 metres thick. By the time you get up to the oculus, they're down to 1.2.
The oculus
At the top of the dome, a perfectly round opening 8.7 metres across is the building's only light source. No glass, never has been. Rain really does fall through. The floor is gently convex with almost invisible drainage holes, which is why it isn't a puddle. On sunny days, a beam of light moves slowly across the walls like a spotlight that forgot to hurry. At noon on April 21, the traditional founding date of Rome, the beam lands directly on the entrance doorway. Whether that was intentional, nobody knows for certain, but I choose to believe it was. The oculus also earns its keep structurally. A solid dome this size would be heavier and crack more easily. The hole takes the stress off the weakest point.
Raphael's tomb and what else is inside
There are several important tombs in the Pantheon. The one everyone looks for is Raphael's. He died in 1520, at 37, which is still devastating. His tomb is in the third niche on the left, marked by a Madonna sculpture by Lorenzetto. The Latin inscription translates roughly as: "Here lies Raphael, by whom Nature feared to be outdone while he lived, and when he died, feared she herself would die." I'd argue it's the most moving epitaph in Rome. Also buried here: two Italian kings (Vittorio Emanuele II and Umberto I) and the painter Annibale Carracci.
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Why the Pantheon survived when other temples didn't
In the Middle Ages, most Roman temples got eaten. Their marble went into new churches. Their bronze was melted down for cannons or church furniture. The Pantheon got lucky. In 609 AD, Emperor Phocas handed it to Pope Boniface IV, who consecrated it as the Church of Santa Maria ad Martyres. Because it was now an active church, nobody quarried it. It didn't escape completely, though. In 1625, Pope Urban VIII (a Barberini, remember the name) had the bronze ceiling of the portico stripped to make cannons for Castel Sant'Angelo and the baldachin inside St. Peter's. The Romans, who never miss a good pun, coined the phrase "Quod non fecerunt barbari, fecerunt Barberini." What the barbarians didn't do, the Barberinis did.
Visiting the Pantheon: what you need to know
Entry is free, but since 2023 you need a timed reservation. Book online through the official site for a small fee, or chance the entrance queue if there are open slots. The best times are early morning, right when it opens at 9, or late afternoon, when the crowd thins and the light through the oculus goes gold. Midday is the most packed, but it's also when the light beam is at its most dramatic. If it's raining, go straight there. Watching rain fall through the oculus and evaporate off the warm floor is one of the strangest, best moments you can have in Rome. Mass is held on Sundays and holy days, so access is limited during services. Photos are fine.
The piazza and what's around it
Piazza della Rotonda, out in front, is worth lingering in. The fountain in the middle is by Giacomo della Porta (1575), with an Egyptian obelisk stuck on top of it in 1711. Honest warning: the cafés on the piazza are a rip-off. Beautiful view, inflated bill. Walk one street back and your espresso drops to a normal Roman price. Behind the Pantheon, the Church of Santa Maria sopra Minerva is absurdly overlooked. There's a Michelangelo sculpture inside (Cristo della Minerva) and a Filippino Lippi fresco cycle, and most visitors will walk straight past the door. A minute further and you're in Piazza di Sant'Eustachio, which many Romans (including me) will tell you serves the best coffee in the city.
Every domed building since, from Brunelleschi's Florence cathedral to the US Capitol, owes something to the Pantheon. None of them beats it. Stand under the oculus, look up, and it's obvious why. Nearly two thousand years in, it's still the best answer Rome ever gave to the question of what a building could be.
