Fortress of the Angels

Few buildings in the world contain as many layers of human history as Castel Sant’Angelo.

In nearly two thousand years, this single structure has been an imperial mausoleum, a medieval fortress, a papal prison, a Renaissance palace, a Napoleonic citadel, and is now a state museum that draws hundreds of thousands of visitors a year.

To walk through it is to walk through Rome’s entire history in a single afternoon.

The building began as a tomb — the grandest private tomb in the ancient world. It became a castle when Rome’s medieval defenders recognised its military potential.

It was decorated as a palace when Renaissance popes retreated here from enemies and summer heat alike. It imprisoned scholars, saints and soldiers in its dungeons. And it was immortalised as the setting for one of the most famous scenes in all of opera.

Every century has left its mark, and every mark is still visible.

Long before the Church took possession of this great structure, it was a major monument honouring the pagan emperors of Rome.
The Emperor Hadrian — one of the greatest rulers of the High Empire, traveller, intellectual, architect, and builder of the villa at Tivoli — constructed an immense cylindrical sepulchre on the west bank of the Tiber in the 130s AD.

Designed in form and scale to rival the great Mausoleum of Augustus further downstream, it was intended to serve as the dynastic tomb of the Antonine imperial dynasty, and eventually housed the remains of emperors from Hadrian himself to Caracalla.

Hadrian’s major architectural innovation was the great spiral ramp that coils inside the massive drum of the tomb, ascending through the concrete structure to the burial chambers above.

Even today, in order to reach the medieval and Renaissance levels of the modern castle, you must walk through the ancient mausoleum. Entering the massive antechamber — once covered in precious marble, its walls lined with niches — you can still make out the space where a colossal statue of the emperor himself once stood.

From there, the giant ramp begins: a slow, rising spiral deep into what feels, counterintuitively, like a descent into the underworld.

At the heart of the structure is the imperial burial chamber itself. Nothing remains of its rich decoration, but the spaces reserved for the sarcophagi of the imperial family are still clearly legible.

Only one ancient object has survived, in unexpected form: the purple porphyry lid of a sarcophagus, believed by some to have been Hadrian’s own, was removed centuries ago and now serves — flipped upside down — as the baptismal font of St. Peter’s Basilica across the river.

An emperor’s tomb providing the vessel for Christian baptism: it is the kind of detail that only Rome, in its endless recycling of the past, could offer.

The fortress takes its famous name from a legend dating to the darkest days of the early Middle Ages.

At the end of the 6th century AD — after Rome’s fall, with the city shrunken to a fraction of its ancient size, streets that had once thronged with a million inhabitants now choked with disease and the bodies of the dead — a terrible plague fell upon what remained of the city.

Pope Gregory the Great, who would later earn the epithet that history has given him, led a solemn procession through Rome, praying to God to spare those who still lived.

As the procession passed the old mausoleum of Hadrian — long fallen into disuse and ruin, its ancient splendours forgotten — Gregory looked up and had a vision of a radiant figure standing atop the massive tomb.

It was an angel, glowing with divine light and brandishing a drawn sword; as the Pope watched, the angel lowered his weapon and sheathed it. The meaning was clear: God’s wrath was satisfied, the plague was ending, and mercy had been granted to the city.

The building has been known as the Castle of the Holy Angel — Castel Sant’Angelo — ever since. The statue of the Archangel Michael that crowns the building today is a bronze version from the early 18th century, replacing earlier marble and bronze versions that stood in the same spot from the early medieval period.

It serves as a reminder, in this resolutely Catholic capital, that divine mercy is present even in the worst of times.

The urban history of Rome is fundamentally a history of re-use, with medieval and Renaissance citizens making pragmatic use of whatever the ancient world had left behind.

Hadrian’s mausoleum, standing 160 feet high on the bend in the Tiber with sheer walls of concrete and brick, was a natural defensive stronghold. Its position on the river bend had been chosen by Hadrian to maximise its visibility; for the Papacy under military threat, it was the perfect place for a fortress.

The tomb was fortified progressively from the late 4th century onwards. Its long history as a military installation produced some of its most atmospheric surviving spaces.

The medieval levels of the building contain vaulted storerooms, guard chambers, and — most notoriously — a series of prison cells where some of the most illustrious names of the Renaissance era were held, including the sculptor and memoirist Benvenuto Cellini, who describes his imprisonment here in vivid, characteristic detail in his famous Autobiography.

One of Castel Sant’Angelo’s most extraordinary features is invisible from outside and largely unknown to visitors who haven’t looked for it: the Passetto di Borgo, a concealed elevated corridor running directly from the Vatican to the castle along the top of the Leonine Wall, allowing the Pope to reach the fortress from St. Peter’s without setting foot in the open streets below.

The Passetto’s most famous use came in 1527, during the catastrophic Sack of Rome by the troops of the Holy Roman Emperor Charles V.

As the imperial army poured through the city’s gates and its soldiers began a nightmare of looting, killing and destruction that would take months to exhaust itself, Pope Clement VII fled through the secret corridor to Castel Sant’Angelo.

The escape was barely managed in time: almost the entire battalion of Swiss Guards who held off the attackers to buy the Pope his head start were massacred on the steps of St. Peter’s, and Clement watched the pillage of his city from the battlements above until a ransom could be negotiated.

The Passetto can be walked by visitors today on selected open days. Even without entering it, the sight of the elevated corridor connecting castle and Vatican — visible from the river and from several points around the Borgo neighbourhood — is one of the most quietly dramatic features of this part of Rome.

Despite its military function, and its continuing role as the Papacy’s ultimate last resort, Castel Sant’Angelo was progressively beautified and refined across the Renaissance period until its upper levels bore considerably more resemblance to a palace than a fortress.

Much of the finalised fortification work was carried out under Pope Alexander VI Borgia, and the interior decorations continued under later popes as styles and tastes shifted from Renaissance to Mannerist.

Pope Leo X commissioned Michelangelo to design the facade of one of the interior courtyards — one of several significant Renaissance artistic presences in the building.

The Sala Paolina, decorated under Paul III Farnese in the 1540s, is among the most spectacular rooms, its walls covered in illusionistic frescoes of a quality that would not shame any of Rome’s great palaces.

By the late 16th century the upper levels of the castle had been so thoroughly transformed that the popes were using them as a summer residence, enjoying the breezes off the Tiber during the brutally hot Roman summers.

Today the castle’s interior offers an extraordinary vertical journey: from the ancient burial chambers in the heart of Hadrian’s mausoleum, up through medieval fortifications and Renaissance courtyard gardens and frescoed papal apartments, to the open terrace at the very summit.

It is one of the most architecturally layered experiences in a city built entirely on layers.

Having ascended through an ancient tomb, medieval fortifications and palatial Renaissance rooms, the pinnacle of Castel Sant’Angelo is an even greater reward. Just below the great bronze angel, the top of the castle opens onto a large panoramic terrace with one of the most dramatic views over the entire city.

To the north-east, those with sharp eyes can make out the top of the Spanish Steps; to the south-east, the distant mass of the Colosseum; and directly westward, more magnificent than from any other viewpoint, the great dome of St. Peter’s Basilica rises against the Roman sky.

Yet while the view from Castel Sant’Angelo’s terrace is reason enough to make the ascent, this exact terrace is also hallowed ground for opera lovers across the world.

On stages from Milan to New York, this precise setting — the battlements, the angel statue, the city spread below — is recreated for Act III of Giacomo Puccini’s Tosca.

It is here that the opera reaches its climax: the painter Cavaradossi has been executed on these battlements; his lover Floria Tosca, having killed the chief of police to save him, discovers that she has been deceived and that Cavaradossi is dead; she throws herself from the parapet rather than face capture.

Puccini set his emotional finale here because he understood that the view from Castel Sant’Angelo — ancient, sublime, and charged with history — was just about the only thing that was a match for his bombastic music.

The Ponte Sant’Angelo connecting Castel Sant’Angelo to the historic centre is one of the most beautiful bridges in Rome, and one of the most remarkable.

The bridge’s ancient structure dates from Hadrian’s reign — the emperor built it specifically as a ceremonial approach to his mausoleum — and its foundations are thus nearly as old as the castle itself.

The ten marble angels that line the parapet were designed by Gianlorenzo Bernini in the 1660s and executed by his pupils, each carrying one of the instruments of the Passion of Christ.

Two of the original angels — the ones Bernini designed himself — were deemed too beautiful to be exposed to the weather and were removed to the church of Sant’Andrea delle Fratte, where they can still be seen; the bridge’s current angels are high-quality copies.

Crossing the Ponte Sant’Angelo towards the castle at night, when the angels are illuminated and the Tiber flows darkly below, is one of the great atmospheric experiences of Rome.