The dramatic history of Castel Sant’Angelo

During the early 2nd century CE, Emperor Hadrian ordered the construction of a large tomb for himself and his family.

Rather than placing it within the traditional sacred heart of Rome, he selected a site just outside the ancient pomerium.

That choice allowed him to create a powerful architectural statement without breaking the city’s religious customs.

The structure took shape between 123 and 139 CE. Hadrian’s engineers designed it as a very large drum set on a square base, topped by an earth mound and crowned with a bronze quadriga.

At its height, the mausoleum stood over 40 metres tall and stretched nearly 90 metres in diameter.

White marble faced the lower portions, while the upper terraces supported gardens and statuary.

A wide spiral ramp wound upward inside the drum, so that visitors could ascend ceremonially to the burial chamber. 

Hadrian died in 138 CE, and his ashes became the first imperial remains to rest within its walls.

His successor, Antoninus Pius, completed the project and ensured that subsequent emperors also received burial there.

The mausoleum housed the remains of emperors including Lucius Verus and Marcus Aurelius.

Although some later sources suggest Caracalla's burial there, modern research questions this claim and casts doubt on where he was finally buried.

In time, however, as Rome entered a time of trouble and repeated invasions, its original funerary purpose faded. 

By the late 3rd century CE, Rome’s leaders began to change important buildings for military use.

Emperor Aurelian strengthened the city’s walls during his reign in the 270s and Castel Sant’Angelo became a main part of that system.

Its location on the western side of the Tiber made it an important position for protecting the Campus Martius and the access roads that led into the city.

By the 5th century, the structure had already undergone major strengthening, with battlements and defensive towers added to its upper levels. 

Through the early medieval period, there were repeated attacks on Rome, including the Gothic siege of 537 CE.

When the Ostrogothic army attacked the city under King Vitiges, Byzantine general Belisarius used the mausoleum as a fortress.

His defenders hurled statues and heavy marble slabs from the battlements onto the attackers.

According to Procopius, the defenders even dislodged and dropped the great bronze peacocks that once decorated the tomb.

As a result, the structure began to lose its original appearance as layers of military fortification, weapon stockpiles, and barracks overtook the tomb architecture. 

As the Papacy gained worldly power during the Middle Ages, Castel Sant’Angelo took on a new role.

By the 10th century, it became the property of the Church and served as both a refuge and a power base for the popes.

Its thick walls and separate location across the river made it ideal for resisting sieges and internal revolts.

In 1277, Pope Nicholas III established a protected passage, the Passetto di Borgo, which connected the Vatican directly to the castle.

This hidden passage allowed popes to flee to safety during emergencies. 

During the sack of Rome in 1527, Pope Clement VII used that very corridor to escape to Castel Sant’Angelo.

Troops of Charles V had took over the city, stealing from churches, slaughtering citizens, and murdering clergy.

From the castle, the pope held out for weeks under siege, relying on its storage rooms, defensive towers, and the loyalty of the few remaining defenders.

In that moment, the fortress earned its reputation as the last redoubt of papal survival. 

As the Renaissance changed Rome, the building underwent another transformation.

Popes such as Alexander VI and Urban VIII ordered repairs that gave the structure its current look.

Defensive walls and gun platforms replaced medieval walls. A chapel and papal apartments took shape within its upper levels.

Frescoes decorated once-plain interiors, and gardens softened the look of the stone walls.

The large statue of the Archangel Michael, which sits atop the structure today, is the result of a 6th-century story.

According to the story, Pope Gregory I saw the archangel sheathing his sword atop the mausoleum, which was though to be a sign of the end of a plague.

That vision gave the building its modern name: Castel Sant’Angelo, or the Castle of the Holy Angel. 

Across the early modern period, popes continued to use the castle as a prison.

Political prisoners, heretics, and enemies of the Papal States often waited in its cells.

The sculptor Benvenuto Cellini spent time imprisoned there. Giordano Bruno, in constrast, was held instead at the Palace of the Holy Office during his trial by the Inquisition.

Executions sometimes took place in its courtyard, where gallows and firing squads left clear proof of the building’s evolving purpose. 

After the unification of Italy in the 19th century, Castel Sant’Angelo lost its role in papal politics because Italian nationalists took it in 1870 when Rome fell to the new Kingdom of Italy.

The Papal States came to an end, and the castle passed into the hands of the Italian government.

Authorities gradually turned it into a museum. During the 20th century, careful repair work aimed to keep both its imperial core and later medieval and Renaissance additions. 

Visitors today can trace the full arc of its history by ascending through its winding corridors and standing in rooms that emperors, generals, popes, and prisoners once used.

From the top, the view across the rooftops of Rome to St Peter’s Basilica offers a good reminder of the structure’s role in protecting both power and faith.

Castel Sant’Angelo is still quite prominent against the Roman skyline, a building that has worn the identities of tomb, fortress, refuge, prison, and museum without ever ceasing to influence the course of the city around it.