The dome of St. Peter’s Basilica was designed by Michelangelo, who became chief architect in 1546. The great double dome is made of brick and is 42.3 metres in interior diameter (almost as large as the Pantheon), rising to 120 metres above the floor.
Uniquely, Michelangelo’s dome is not a hemisphere, but a parabola: it has a vertical thrust, which is made more emphatic by the bold ribbing that springs from the paired Corinthian columns, which appear to be part of the drum, but which stand away from it like buttresses, to absorb the outward thrust of the dome’s weight. Above, the vaulted dome rises to Fontana’s two-stage lantern, capped with a spire.
Photograph by Galen Crout