Due to its unique features, Castel Sant’Angelo can be considered a monument, an archaeological area and a museum at the same time. The building has had an extremely varied use during its complex history: after being erected as an imperial mausoleum, it later became a fortified residence, prison and, finally, a monument-museum.

Built in the second century AD by the Roman emperor Hadrian as a funeral mausoleum for himself and his family, the monument – known here as Mole Adriana – was later included in the city walls of Rome and transformed into a sort of fortress for defending the city, acquiring the epithet of castellum. In the early mediaeval period, it also took on the name of sancti Angeli thanks to a legend, according to which, in 590, Pope Gregory the Great had a vision of the archangel Michael here, who sheathed his sword, symbolising the end of the plague that afflicted the city.

Its proximity to San Pietro, its strategic position, its closed interiors and its imposing size made Castel Sant’Angelo the centre of political interests. Its fate was inseparably linked to that of the Church when the keys of the building were handed over to Pope Urban V in 1367, to urge him to return to Rome from exile in Avignon.

Since then, numerous architectural interventions have been carried out with the aim of strengthening its defensive structure on the one hand, with the construction of the ramparts and the pentagonal wall, and, on the other, to make it an increasingly magnificent papal residence, reaching the peak of its splendour under Paul III Farnese (1534-1549).

Starting in the seventeenth century, Castel Sant’Angelo gradually lost its role as a papal residence and became almost exclusively a political prison. After being included in the Italian State property in 1870 as a military prison and barracks, it became a National Museum in 1925. At that time, extensive works had already begun to reorganise and restore the site, acquire works and collections and set up various rooms.