Castel Sant'Angelo
The Castel Sant'Angelo is towering cylindrical building in Rome, initially commissioned by the Roman Emperor Hadrian as a mausoleum for himself and his family. It was erected on the right bank of the Tiber, between AD 135 and 139. Originally, the mausoleum was a decorated cylinder, with a garden top and the golden quadriga of the emperor. In 401, the mausoleum was converted into a military fortress and included by Flavius Augustus Honorius in the Aurelian Walls. The popes converted the structure into a castle, from the 14th century; Pope Nicholas III connected the castle to St. Peter's Basilica by a covered fortified corridor called the Passetto di Borgo. The fortress was the refuge of Pope Clement VII from the siege of Charles V's Landsknecht during the Sack of Rome (1527), in which Benvenuto Cellini describes strolling the ramparts and shooting enemy soldiers.
The Papal state also used Sant'Angelo as a prison; Giordano Bruno, for example, was imprisoned there for six years. As a prison, it was also the setting of Giacomo Puccini's Tosca from whose ramparts the namesake of the opera leaps to her death.
An 18th century bronze angel sheathing a sword surmounts the tomb; legend holds that an angel appeared atop of the mausoleum, sheathing his sword as a sign of the end of the plague of 590, thus lending the castle its present name.
Now the photogenic castle is a museum, Museo Nazionale di Castel Sant'Angelo. The Ponte Sant'Angelo, providing a scenic approach from the center of Rome and the right bank of the Tiber, dates also from Imperial Rome and is renowned for its Baroque statuary of angels holding aloft elements of the Passion of Christ.


From: www.wikipedia.org