The area where the church stands today covered much of the ancient Baths of Diocletian, but in 1561 Pope Pius IV, on the advice of the priest Antonio Lo Duca, had a magnificent place of worship built there. The location was chosen on account of a vision that the same priest had had. On this very spot he had, in fact, seen a beam of light containing the seven martyrs killed during the baths’ construction. For this reason Lo Duca had wanted the new church to be dedicated at any cost to the Martyrs and Angels, to whom he had a special devotion.
Michelangelo, by then 86 years old, was entrusted with this task, and he planned the structure to integrate the sacred building and the baths in masterful fashion. The concave façade, for example, is none other than one of the ancient apses of the thermal calidarium.
On the splendid flooring, Pope Clement IX inaugurated a 45 metre sundial in 1702 (indicating midday, the changing seasons and even some constellations). It was produced by Francesco Bianchini, inspired by the astronomer Gian Domenico Grassini.
Today the basilica is known as the site dedicated to official celebrations of the Republic of Italy, precisely on account of its historical, religious and cultural significance, which has made it possible for it to become a point of reference for the spiritual unity of the nation.