Emperor Hadrian had it built in 130 A.D. as his mausoleum.
It held the remains of the Imperial family until Caracalla. It rises close to Victor Emmanuel II bridge in lungotevere Castello. Originally it was much different from today's. Under emperor Aurelian it was strongly fortified, in the 11th century a tower was added and in 1277 it was occupied by the Pope who added to it some apartments.
The actual name roots in an old legend on the bronzy 18th century angel, telling that during the dreadful pestilence of 590 an angel appeared sheathing his sword as a sign of granted grace. It was Used as shelter for popes and as jail. To make it safer in 1277 it was joined to the Vatican by the famous "Passetto".

This long fortified passageway allowed the pope to walk safely from the Vatican to Castel Sant'Angelo. Today it is a Museum (National Museum in Castel Sant’Angelo). There are collections of weapons and documents about the history of the castle. All rooms can be visited, from the jail to the pope's apartments and all the numerous fully adorned rooms. You can see: Apollo's room with frescoes by P. del Vaga’s school; Leo X's chapel with Renaissance sculptures; Clemente VII's rooms with works by G. Romano, T. Cats, L. Signorelli and others; Paul III's loggia by R. da Montelupo; Giulio II's loggia by Bramante; Paul III's apartment with the Paoline room decorated by P. del Vaga, D. Beccafumi and others; Adrianeo’s room and the Festoons' room with ST. Jerome painted by L. Lotto.