The largest unreinforced concrete dome in the world, open to the sky
Rebuilt by the emperor Hadrian around 125 AD on the site of an earlier temple by Agrippa, whose name is still on the façade, the Pantheon is the best preserved building of ancient Rome. Its secret is the dome: 43.3 metres in diameter, exactly the same as its height, it is still the largest dome in the world made of unreinforced concrete, lighter towards the top thanks to the use of pumice stone.
At the centre opens the oculus, a hole nine metres wide through which light, and sometimes rain, falls into the temple; small holes in the floor let the water drain. Transformed into a church in 609, the Pantheon has survived intact and holds the tombs of Raphael and of the first kings of Italy. In front of it, Piazza della Rotonda with its fountain and obelisk is one of the liveliest squares in Rome.
Tip: since 2023 entry requires a small ticket; on the feast of Pentecost, thousands of red rose petals are dropped through the oculus.
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