Castel Sant'Angelo, also known as the Mausoleum of Hadrian, is a monument of Rome, located on the right bank of the Tiber in front of Poni Aelius, connected to the Vatican State through the fortified corridor of the "Passetto" Begun by Emperor Hadrian in 125 as his funeral mausoleum, inspired by the full august mausoleum, was completed by Antonino Pio in 139. It was built in front of Campo Marzio, to which it was joined by a specially built bridge, the Elio Bridge. The mausoleum consisted of a cubic base, lined with lunge marble, with a decorative frieze with oxen heads (Bucrani) and angular lobes. In the frieze facing the river, the names of the emperors buried inside were read. Always on this side was the entrance archive of Adriano; the dromos (access passage) was entirely covered with old yellow marble. Above the base cube was a drum made of pepper and cement work, all covered with travertine and slotted grooves. Around the mausoleum was a bronze walled bronze pavement wall decorated with peacocks, two of which are kept in the Vatican. Inside, light wells light up the marble brick helicopter ramp connecting the dromos to the cell in the center of the mound. The latter, square and entirely covered with polychrome marbles, was surmounted by two other rooms, perhaps also used as burial cells. The Mausoleum housed the remnants of Emperor Hadrian and his wife Vibia Sabina, Emperor Antonino Pio, his wife Faustina maggiore and three of their children, Lucio Elio Cesare, Commodo, Emperor Marco Aurelio and three other children. In 403 the Emperor of West Honorio included the building in the Aurora Walls: from that momen over the Tiber to the defense of Rome. It was then that the mausoleum was first mentioned with the name of castellum. The mausoleum took its present name in 590. In that year Rome was afflicted by a serious plague, to turn away which was organized a solemn penitential procession involving the same pope Gregory I. When the procession came near the Mole Adriana , the pope had the vision of the archangel Michael refining his sword. The vision was interpreted as a celestial sign preannunciating the imminent end of the epidemic. In 1542 Paolo III restructured the castle by architects Raffaello Sinibaldi from Montelupo and Antonio da Sangallo il Giovane, from 1520 the chief architect of the San Pietro factory. The decoration of the rooms is entrusted to Perino del Vaga and to Luzio Luzi da Todi, with the collaboration of Livio Agresti from Forlì. The great pentagonal bastioned enclosure, the last episode of a long history of fortifications, began under Pope Paul IV 1555 and 1559, concluded under his successors by Francesco Laparelli. Between 1667 and 1669, Clement IX placed ten marble angels on the Ponte Helius: from then on the bridge is called Sant'Angelo. To commemorate the event that gave its present name to the structure, the statue of an angel crowns the building. Originally it was a wooden statue that ended up for consumption; the second marble angel was destroyed in 1379 in a siege and replaced in 1453 by a marble angel with bronze wings. This angel was destroyed in 1497 by a lightning strike that exploded a powder in the castle and was replaced with a bronze gilded but in 1527 it was cast to make its cannons. Finally it was the turn of a marble statue with the bronze wings of Raffaello da Montelupo dating back to the sixteenth century and currently visible in the Courtyard of the Angel and then in 1753 came the present bronze angel of Peter Anton von Verschaffelt.