The Castel Sant'Angelo, also known as The Hadrian Mausoleum, was constructed 130AD-139AD on the edge of the River Tiber by Emperor Hadrian for himself, his family and his successors interment. The mausoleum has a cylindrical colonnaded drum, 64 meters in diameter, on top of an 89 meter wide square base which was covered with lush planted gardens and trees. Situated on the right bank of the river, the Ponte Sant'Angelo connects it with the rest of the city.
Over the years the function and appearance of the Castel Sant'Angelo changed. In the middle Ages additional towers and fortified walls were constructed. It became an impenetrable defensive bastion during the barbaric invasions, and was incorporated into the city walls (270-275AD), protecting the northern entrance of Rome. Most of the tombs and precious decoration were destroyed when the structure became a fortress in 401 and the royal ashes are thought to have been lost during the Alaric sacking of Rome.
For the protection of the papal community a secret, fortified passage way, Passetto di Borgo, was constructed (14th century), connecting the Vatican to the Castel Sant'Angelo. During the Renaissance a treasury room was located in the center of the structure to keep the pope's valuables safe. The structure became a storage space for food, water and supplies to be used in the event of an emergency. There was even a granary and mill incorporated into the fortified structure.
The mausoleum was used as a brutal prison where prisoners were tortured and starved. At one time executions were carried out in the inner courtyard. Famous inmates included Benvenuto Cellini, Cagliostro and Giordana Bruno.
Originally a statue of the Emperor riding a chariot like the sun god, would have stood on the central tower this was replaced later by a statue of an angel, hence the name of the castle. Today an 18th century bronze statue of the Archangel St. Michael has replaced the original marble angel and adorns the mausoleum in memory of a plague which raged through Rome in 590AD only to end when an apparition of an angel appeared above the mausoleum.
When the Italian State was established the fortress was used to house soldiers and today the much loved iconic structure has been restored and recreated. It is visited by tourists who come to see the National Museum of Castel Sant'Angelo. Visitors approach the structure by following a 400 foot long spiral ramp. Visitors can see the beautiful rooms used by the pontiffs with delicate frescoes and on lower floors they can see the prisons and torture chamber.