The dome was designed by Michelangelo, who worked on the construction of the basilica beginning in 1547. By the end of his long life (he died at 89 in 1564), construction had reached the drum of the dome, which alternates highly prominent double columns with gabled windows. Then, Giacomo Della Porta, Michelangelo’s pupil, took over the direction of the work, raising the vault of the dome about 7 metres and completing it in 1590, in just 22 months, under the pontificate of Pope Sixtus V.
The dome has a double calotte, with an inner diameter of 42.56 metres and it measures 136.57 metres from the base to the top of the cross. The lantern is 17 metres high.
This dome was used as a model for other domes in the western world. Among such domes, although built according to different techniques, are those of Saint Paul’s in London (1675), Les Invalides in Paris (1680-1691) and the Capitol building in Washington (1794-1817).