Castel Sant ' Angelo The Mausoleum of Hadrian , usually known as Castel Sant ' Angelo ( English : " Castle of the Holy Angel " ) , is a towering cylindrical building in Parco Adriano , Rome , Italy . It was initially commissioned by the Roman Emperor Hadrian as a mausoleum for himself and his family . The building was later used by the popes as a fortress and castle , and is now a museum . The Castel was once the tallest building in Rome . Hadrian ' s tomb . The tomb of the Roman emperor Hadrian , also called Hadrian ' s mole , was erected on the right bank of the Tiber , between 130 AD and 139 AD . Originally the mausoleum was a decorated cylinder , with a garden top and golden quadriga . Hadrian ' s ashes were placed here a year after his death in Baiae in 138 AD , together with those of his wife Sabina , and his first adopted son , Lucius Aelius , who also died in 138 AD . Following this , the remains of succeeding emperors were also placed here , the last recorded deposition being Caracalla in 217 AD . The urns containing these ashes were probably placed in what is now known as the Treasury room deep within the building . Hadrian also built the Pons Aelius facing straight onto the mausoleum – it still provides a scenic approach from the center of Rome and the right bank of the Tiber , and is renowned for the Baroque additions of statues of angels holding aloft elements of the Passion of Christ . Destruction . Much of the tomb contents and decorations have been lost since the building ' s conversion to a military fortress in 401 and its subsequent inclusion in the Aurelian Walls by Flavius Augustus Honorius . The urns and ashes were scattered by Visigoth looters during Alaric ' s sacking of Rome in 410 , and the original decorative bronze and stone statuary were thrown down upon the attacking Goths when they besieged Rome in 537 , as recounted by Procopius . An unusual survivor , however , is the capstone of a funerary urn ( probably that of Hadrian ) , which made its way to Saint Peter ' s Basilica and was incorporated into a massive Renaissance baptistery . The use of spolia from the tomb in the post - Roman period was noted in the 16th century — Giorgio Vasari writes : Legend holds that the Archangel Michael appeared atop the mausoleum , sheathing his sword as a sign of the end of the plague of 590 , thus lending the castle its present name . A less charitable yet more apt elaboration of the legend , given the militant disposition of this archangel , was heard by the 15th - century traveler who saw an angel statue on the castle roof . He recounts that during a prolonged season of the plague , Pope Gregory I heard that the populace , even Christians , had begun revering a pagan idol at the church of Santa Agata in Suburra . A vision urged the Pope to lead a procession to the church . Upon arriving , the idol miraculously fell apart with a clap of thunder . Returning to St Peter ' s by the Aelian Bridge , the Pope had another vision of an angel atop the castle , wiping the blood from his sword on his mantle , and then sheathing it . While the Pope interpreted this as a sign that God was appeased , this did not prevent Gregory from destroying more sites of pagan worship in Rome . Papal fortress , residence and prison . The popes converted the structure into a castle , beginning in 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 e during the Sack of Rome ( 1527 ) , in which Benvenuto Cellini describes strolling the ramparts and shooting enemy soldiers . Leo X built a chapel with a " Madonna " by Raffaello da Montelupo . In 1536 Montelupo also created a marble statue of Saint Michael holding his sword after the 590 plague ( as described above ) to surmount the Castel . Later Paul III built a rich apartment , to ensure that in any future siege the Pope had an appropriate place to stay . Montelupo ' s statue was replaced by a bronze statue of the same subject , executed by the Flemish sculptor Peter Anton von Verschaffelt , in 1753 . Verschaffelt ' s is still in place and Montelupo ' s can be seen in an open court in the interior of the Castle . The Papal state also used Sant ' Angelo as a prison ; Giordano Bruno , for example , was imprisoned there for six years . Another prisoner was the sculptor and goldsmith Benvenuto Cellini . Executions were performed in the small inner courtyard . As a prison , it was also the setting for the third act of Giacomo Puccini ' s " Tosca " ; the eponymous heroine of the opera leaps to her death from the Castel ' s ramparts . Museum . Decommissioned in 1901 , the castle is now a museum , the Museo Nazionale di Castel Sant ' Angelo .