Castel Sant’angelo is located on the bank of the Tiber River, which was designed as a mausoleum for Hadrian, then the city wall was built around it, used as a fortress, papal home, and then a barracks and military prison. It contained the remains of Hadrian, and all other successors until Caracalla. This build is designed after Augustus’ Mausoleum, which was built a century before. Construction started in 123 AD, and finished in 139 AD, during Antoninus Pius’ rule. The building rests on an eighty-nine meter wide base, and the building itself is a drum with a diameter of sixty-four meters.

       Because it is on the right side of the Tiber River, a bridge links it to the city, the bridge being the Pons Aelius. From 270 to 275 AD, Hadrian’s mausoleum was incorporated into the Aurelian Wall, and was fortified to protect Rome. This is where the name Castel Sant’angelo was born, because from then on, it was used as a fortress, later received from the Pope, to use the building as a castle if he is ever in danger. There is a secret (maybe not so secret) passage that connects the Castel Sant’angelo to the Vatican, which was used by Pope Clement VII and his guards to escape during the sack of Rome in 1527. Although it is a fortress, it is very extravagant in its interior design, many rooms are decorated with frescoes, and below these rooms there are prisons and even a torture chamber. Due to the fact that the building is a cylinder, the stairs are spiraling, and the lower levels of the building contain the actual mausoleum area.

            The top of the fortress is decorated with an enormous statue of an angel, built by Pieter Verschaffelt in the eighteenth century. An early version was built from marble, but the current version is made of bronze. The angel is the archangel Michael, who was said to have appeared on the top of the fortress in the year 590, ending the plague that infested Rome. Due to this miraculous event, the building received its title: Castel Sant’angelo, meaning Castle of the Angel Saint, in Michael’s honor.