The dome of Saint Peter’s Basilica: facts and curiosities

Historical events

The dome of Saint Peter’s Basilica has been declared a site of cultural heritage of humanity, it is an icon of the Eternal City and a symbol of the Catholic Church.

It’s creation is thanks to Michelangelo Buonarroti’s plans, (drawn up at no cost by the Maestro) who died in 1564, leaving the construction unfinished.

For years it was impossible to continue such a complex undertaking: the double-shell structure and walkable cavity (with dormer windows to illuminate the inhabitable space) was born based on the model of Brunelleschi's dome for Florence Cathedral, Brunelleschi being one of the fathers of the Italian Renaissance, and therefore for the time, it was a totally avant-garde project.

Pope Sixtus V (1585-90) managed the construction site by entrusting it to the architects Giacomo Della Porta and Domenico Fontana, who with 800 workers and over 22 months of construction - performed day and night, even eating their meals on the scaffolding – managed to finish the work in the summer of 1590.

The climb to the Dome is a unique experience that is definitely worth trying. The entrance is in the right courtyard of the basilica; you can climb 551 steps on foot, or save a little effort with the lift, to get to the level of the drum, from where you can enjoy both the outdoor terrace at roof level of St. Peter's basilica, as well as the colourful mosaics adorning the dome itself. From here you continue on foot for another 320 steps to the panoramic terrace, which allows a 360° view of the city of Rome: a truly breath-taking viewpoint.

Clement VIII (1592-1605) completed the structure in the years following the death of Sixtus V. The interior is decorated with the four Evangelists in the pendentives that support the dome, on the drum the inscription citing the gospel of the "handing over the keys" can be read on the drum (the reason of the primacy of Peter), while the actual dome is adorned with mosaics by Cavalier D'Arpino (the maestro of Caravaggio) with 96 sacred figures; the closing ring contains the inscription in memory of Sixtus V, and God the Father is in the smaller dome of the lantern.

The dome is covered with lead plates, with a lantern surmounted by a golden bronze sphere with a cross.

Curious facts

The dome weighs 14,000 tons; its external height is 133.30m and its internal diameter is 41.50m: It is the second largest dome in Rome, given that the Pantheon takes first place (II century AD).

In 1809 a lightning rod was added to protect the dome from lightning strikes.

It may seem impossible, but the sphere at the top of the dome is habitable: about a dozen people can enter it and up until the 1950s it was possible to visit it by climbing a ladder and passing through a narrow entrance. It was here in 1845 that Pope Gregory XVI accompanied the Tsar of Russia Nicholas I, who enthusiastically signed his name upon it.

Any Roman citizen showing guests around his or her home city knows that by taking them to via Niccolò Piccolomini (Aurelio district), they will be stunned and delighted by phenomenon known as prospective illusionism. In this street you can enjoy a spectacular view of the dome, yet due to this extraordinary optical effect, the closer you get to the dome, the farther away it appears, and vice versa. A truly incredible experience!