The Castle of Sant'Angelo (St Angelus), whose mighty block still dominates the panorama of Rome, originally served as a tomb for emperors and was converted into a fortress only in the Middle Ages. The castle is also called Hadrian's Mausoleum. To connect this majestic monument with the Champ de Mars, the Sant'Angelo Bridge was built. It consists of three huge central arches and two inclined platforms supported by three arches on the right bank and two on the left bank.
The construction scheme of the mausoleum, incorporated into the building of Castel Sant'Angelo since the Middle Ages, has remained largely unchanged. The building stands on a huge quadrangular base, each side of which is 89 metres long and 15 metres high. On this base is a cylindrical drum 21 metres high, surrounded by radial walls. On top of this drum is a huge earthen hill planted with trees, and marble statues are placed on its edges. The outside of the building is lined with moonstone (a type of marble) with tablets embedded all round the circumference of the wall, bearing the names and titles of those who were buried inside the mausoleum. The burial room, located in the very centre of the massive drum, is square in shape with three rectangular niches. In this room were placed urns with the ashes of emperors.
Perhaps as early as 403, Emperor Honorius included this building in the bastion of the Aurelian defensive wall. After becoming a fortress, it was besieged by the Goths led by Vitigus in 537. Its transformation into a castle took place in the 10th century. Today the castle is a strong fortress on a square base with four round towers at the corners, bearing the names of the apostles: St Matthew, St John, St Mark and St Luke. During the pontificate of Benedict IX, a cylindrical body was placed on the base, repeating the construction scheme of Hadrian's Mausoleum. Further changes were introduced to the castle during the reigns of Popes Alexander VI and Julius II. Under the latter, a loggia was built in the upper part of the castle as a framing of the pope's apartments.
At the top there is a viewing terrace, above which hovers the Angel, who gave the castle its name, and who, according to legend, on his wings brought a saving deliverance to Rome from the terrible plague epidemic that raged during the pontificate of Gregory the Great. Inside the castle, the National Military Museum and the Museum of Art are now located.
