Built by the emperor Adrian in 123 A.D. as a mausoleum for himself and his imperial dynasty. The original work was very different from the one you can see today; it turned into a castle in the X century; in 1277 it became property of the Church, that joined it through the famous "passetto" to the Vatican walls. The passetto is a long fortified corridor that allowed the the pontiffs to pass from the Vatican Palaces to the castle. The name of Castel Sant'Angelo dates back to the XII century and originates from an ancient legend that tells the story of the plague in Rome in 590; according to this story the plague came to an end thanks to an angel that alighted upon the mausoleum and made the gesture of replacing the sword in the sheath, symbolizing the accorded Grace. To remember this event, not only the name of the monument was changed, but the statue in honor of the angel was put on the top.