Nineteen centuries of history look down on us from one of the greatest monuments of ancient Rome, the Mausoleum of Hadrian, which in the Middle Ages was transformed into an impregnable fortress that withstood countless sieges, including th one of the Landsknechts.
At the beginning of the 2nd century AD there was no more room in the Mausoleum of Augustus, the first great dynastic tomb in Rome. The last emperor to be buried there was Nerva, while Trajan (who died in 117 AD) was allowed to be buried within the city walls, and his urn was placed in the base of Trajan’s Column.
The Mausoleum of Augustus stood in the Campus Martius, but there was not enough space for another building of that size. So Hadrian decided to build the new dynastic tomb in the same area, but on the opposite bank of the Tiber, where the Horti Domitiae were, which had long belonged to the Imperial House. To reach them, he built the Pons Aelius, which was the monumental and scenographic access to the tomb.
From an architectural and design point of view, enormous problems had to be faced and solved, because the land on the river bank was marshy and unstable. Therefore, foundations over seven meters deep were made with wooden and cast piles, found during the demolitions of the late nineteenth century.
The Pons Aelius was inaugurated in 134 AD by Hadrian himself, while the Mausoleum required longer construction times, and was inaugurated by Antoninus Pius, Hadrian's successor, in 139 AD.
Surrounded by a bronze gate decorated with gilded bronze peacocks, the Mausoleum had a large square Base podium with the only access door on the south side, aligned with the Pons Aelius. Above was the actual tomb, that is, a large circular building surrounded by columns, similar to the Mausoleum of Caecilia Metella.
The door led into the large Lower Vestibule, at the end of which one entered the Spiral ramp, one hundred and twenty-five meters long, which with a spiral path rose in height until it reached the Upper Vestibule, ten meters higher.
A short corridor (now obliterated) led into the Hall of the Burial Urns which was originally closed. A staircase led instead to the Upper square where another square base, the Substructure Podium, supported a circular Temple crowned by an enormous bronze Quadriga of the Sun driven by the emperor Hadrian depicted as Sol Invictus.
In 590, with the legendary apparition of the Archangel Michael to Pope Saint Gregory the Great, which put an end to the terrible plague of that era, the Mausoleum changed its name and became Castel Sant’Angelo.
Due to its strategic location and tower-like shape, in late antiquity the Mausoleum became a fortress, and resisted the first ferocious sieges of the Visigoths in 410 and the Vandals in 454, who devastated the city.
In 537 AD, to face the siege of the Goths of Vitige, General Belisarius broke the sculptures of the Mausoleum into pieces and threw them on the besiegers. From tht time on it began the spoliation of the Mausoleum, which culminated in 1379 when the Municipality authorized the removal of its travertine covering to pave the streets and squares of Rome.
At the end of the fourteenth century, the Castle was transformed into the «most fortified of fortresses», digging a moat all around the circular building, walling up the original entrance door with the Lower Vestibule and the Spiral Ramp, and transforming the Hall of the Burial Urns into a casemate.
A new entrance was created higher up, with a drawbridge, building the Diametrical Ramp that still leads to the upper floors of the Castle, where the Renaissance popes, starting with Alexander VI, built magnificent apartments calling upon the greatest artists of their time to create them.
At the end of the eighteenth century, with the French occupation, there was the definitive decline of the Castle, transformed into a prison and barracks. It all culminated with the unfortunate demolitions of the late nineteenth century: during the construction of the new raised riverbanks of the Lungotevere, the original ramps of the Aelius Bridge were rediscovered and were mercilessly demolished to quickly complete the work.
The original entrance with the Lower Vestibule and the Spiral Ramp were also rediscovered, and all the medieval additions in the Hall of the Burial Urns were demolished.
Recent restoration work and the opening of the Antiquarium with splendid sculptural fragments have made Castel Sant’Angelo one of the most beautiful and interesting Museums in Rome.
Like all great Roman monuments, Hadrian's Mausoleum was designed and built to last forever, and in fact it has defied the millennia, overcoming natural and human catastrophes such as floods, earthquakes, wars and looting.
This and much more can be read in Marina De Franceschini's book «Castel Sant'Angelo. Mausoleum of Hadrian, Architecture and Light», (English edition) which traces its thousand-year history.