Castel Sant’angelo in Rome was initially commissioned by Emperor Hadrian as a mausoleum for himself and his family. The Elio Bridge was built specially in 135 BC to connect Campo Marzio with the tomb.
The name of the monument is attributable to the large statue of an angel on the top terrace, in memory of the apparition in the 17th century of an angel who announced the end of the plague to Pope Gregory I.
The bell “della Misericordia”, near the statue of the angel, was originally rung to inform the people of executions.
The Vatican Corridor, built at the end of the thirteenth century, connected Castel Sant’Angelo to the Vatican Palace and acted as a raised passageway for the Pope to escape in the event of a siege.