Castel Sant'Angelo: 24 milestones, 139 AD to 1925
The complete documented chronology of one of Rome's most consequential buildings — from the deposition of Hadrian's ashes to the establishment of the National Museum — based on the official 24-milestone timeline published by the Direzione Musei Nazionali di Roma.
Eras
The 24 milestones
- 139 ADRoman
Deposition of Hadrian's ashes
The original nucleus of the building was constructed by order of Emperor Publius Aelius Hadrianus as a monumental tomb for himself and his family. The mausoleum stood in a suburban area on the right bank of the Tiber and was connected to the city by Pons Aelius, today Ponte Sant'Angelo. Hadrian's ashes were placed inside in 139 AD, one year after his death, beginning the long imperial use of the structure as the resting place of Roman emperors through Caracalla.
The history of Ponte Sant’Angelo → - 271Roman
Aurelian incorporates the tomb into the city walls
Emperor Aurelian, facing repeated barbarian incursions, ordered the construction of a new defensive wall around Rome. Hadrian's mausoleum, by then almost a century and a half old, was deemed strategically valuable and incorporated directly into the new walls. This was the first conversion of the imperial tomb into a defensive structure — a transformation that would define its purpose for the next sixteen centuries.
- 547Medieval
The Creation of Borgo
During the Gothic War, the Ostrogothic king Totila used the mole of Hadrian as the bastion of a fortified citadel built around it, called Borgo. Defenders are said to have hurled the marble statues that decorated the mausoleum down onto the besieging Byzantine army — the destruction that stripped the building of its original imperial sculpture. The neighbourhood that grew around it kept the name Borgo, still used today.
- 608Medieval
Dedication to the Archangel Michael
Pope Boniface IV consecrated the sepulchral chamber of Hadrian to the cult of the Archangel Michael. Centuries later, the legend would spread that during the procession Pope Gregory the Great led against the plague (590–604) across Pons Aelius, Michael appeared on the summit of the building, sheathing his sword to signal the end of the pestilence then afflicting Rome. The legend gave the building its definitive name: Castel Sant'Angelo.
- 998Medieval
Crescentius II revolts against the emperor
A strategic point for control of the city, between the 9th and 14th centuries the mole was contested by the most powerful aristocratic Roman houses. Crescentius II's revolt against Emperor Otto III is the most documented episode, but the pattern was constant: whoever held the castle held a key piece of papal power. The structure was modified, fortified, and changed hands repeatedly during this period.
- 1277Medieval
The Passetto di Borgo is begun
Pope Nicholas III Orsini, identifying the strategic value of an emergency route between the Vatican and the castle, ordered the construction of an elevated corridor known as the Passetto. The 800-metre walkway, built on top of the existing 9th-century Leonine Walls, would allow popes to flee from the Vatican Palace to the safety of Castel Sant'Angelo in moments of crisis. It would prove decisive in 1494 (Charles VIII) and again in 1527 (Sack of Rome).
The Passetto di Borgo: full history → - 1377Medieval
The papacy takes definitive possession
After the return of the papacy from Avignon, Castel Sant'Angelo passed permanently into papal hands. From this date forward, it would be a papal property without interruption until 1870. The transition closed the medieval period of contested ownership and opened the Renaissance era, when the castle would be transformed from a defensive structure into a residence, treasury, and symbol of papal power.
- 1395Medieval
The ancient tomb becomes an impregnable fortress
Niccolò Lamberti, architect of Pope Boniface IX (1389–1404), undertook a series of functional modifications that adapted the mole to the new realities of military technology. Walls were thickened, openings reduced, defensive platforms added. By the end of the works, what had been an imperial tomb was now what contemporary chroniclers called an inespugnabile fortezza — an unconquerable fortress.
- 1447–1455Medieval
Niccolò V begins the corner towers
Pope Nicholas V launched the construction of four corner towers, transforming the castle's silhouette from a pure cylinder into the recognisable tower-flanked shape that would dominate Roman views for the next centuries. The towers gave the castle proper artillery emplacements at each corner of the surrounding bastion, multiplying its defensive capacity and turning it into one of the strongest fortifications in central Italy.
- 1492–1503Renaissance
Alexander VI strengthens and embellishes
With Alessandro VI Borgia, the architect Antonio da Sangallo the Elder erected the four bastions dedicated to the Evangelists, which incorporated the towers of Niccolò V and surrounded the building with a star-shaped enceinte. A moat was excavated around the walls, and a turret was raised between the castle and the bridge. Pope Alexander also commissioned a sumptuous papal apartment frescoed by Pinturicchio, of which nothing now remains — lost in later renovations.
- 1503–1513Renaissance
A luxurious residence for Julius II
Pope Julius II (1503–1513) ordered the creation of an open loggia facing the river and the bridge, designed to serve the papal apartment. He also added the Stufetta, a small bath chamber later decorated by Giovanni da Udine — a private space of extraordinary refinement that survives today and reveals how the castle had become, by this point, as much a residence as a fortress.
- 1523–1534Renaissance
The Sack of Rome
Pope Clement VII (1523–1534) took refuge in the castle together with the papal court to escape the imperial Landsknechts. For seven months, while Rome was sacked below, the castle was the only ground still in papal hands. Pope Clement reached it through the Passetto di Borgo just minutes before the troops of Charles V breached the Vatican — a flight that would shape European political memory for the next century.
The Sack of Rome 1527: full story → - 1538–1539Renaissance
The imprisonment of Benvenuto Cellini
The Florentine sculptor and goldsmith Benvenuto Cellini was imprisoned in the castle on charges of having stolen pontifical jewels during the Sack of Rome. His escape — by tying bedsheets together and lowering himself down the outer wall — became one of the most famous episodes of Italian Renaissance literature, retold by Cellini himself in his autobiography. He broke his leg on landing and was recaptured shortly afterwards.
Cellini's escape: full story → - 1545–1547Renaissance
Decoration of the Sala Paolina
Perin del Vaga, with a large team of artists, executed the elaborate plastic-pictorial complex of the salon of Paul III Farnese. The Sala Paolina is the most lavish room in the castle and one of the most important Mannerist interiors in Rome — a celebration of papal power that converted what had been the central reception hall of the castle into a setting fit for receiving European princes.
- 1561Renaissance
Beginning of the pentagonal enceinte
Pope Pius IV ordered the construction of the outer pentagonal walls, the second ring of defences that gave the castle its current footprint. The pentagonal shape was the state-of-the-art military architecture of the late 16th century, designed to deflect cannon fire and provide overlapping fields of artillery coverage. The bastions named after the four Evangelists — Matthew, Mark, Luke and John — anchor each corner.
- 1599Renaissance
The execution of Beatrice Cenci
In Piazza di Ponte, on the left bank of the Tiber across from the castle, Beatrice Cenci was beheaded for the murder of her abusive father, after the death sentence handed down by Pope Clement VIII. The bodies of the condemned remained on display as a warning. Her case became a lasting symbol of injustice, inspiring works by Shelley, Stendhal, Dumas, Moravia, and Artaud over the next four centuries.
Beatrice Cenci: full story → - 1628Baroque
Urban VIII promotes the star-shaped recinto
Pope Urban VIII Barberini commissioned further reinforcement of the outer star-shaped enceinte, modernising the artillery emplacements and adding new ravelins. This was also the period when the Pope, famously, ordered the bronze beams of the Pantheon's portico stripped to be melted down for the cannons of Castel Sant'Angelo — prompting the Roman pasquinade quod non fecerunt barbari, fecerunt Barberini ("what the barbarians did not do, the Barberini did").
- 1667–1669Baroque
Bernini designs a new parapet for the bridge
Under Pope Clement IX (1667–1669), Gian Lorenzo Bernini designed a new balustrade for Ponte Sant'Angelo, ornamented with ten figures of angels carrying the instruments of the Passion. Bernini personally sculpted only two of them — the Angel with the Crown of Thorns and the Angel with the Superscription — which were judged too beautiful to leave outdoors and were eventually moved to the church of Sant'Andrea delle Fratte. The eight remaining angels are by his workshop.
Ponte Sant'Angelo: Bernini's bridge of angels → - 1752Baroque
Verschaffelt sculpts the statue of the Angel
Over the centuries, the statue at the summit of the castle had been replaced multiple times. The current bronze figure — the sixth version — was executed by the Flemish sculptor Peter Anton Verschaffelt and installed in 1752, replacing earlier versions that had been damaged by lightning, war, and weather. Verschaffelt's Angel still crowns the castle today, sword sheathed in the gesture of the Gregorian legend.
- 1789Baroque
The imprisonment of Cagliostro
Accused of sorcery and freemasonry, the famous adventurer and alchemist Giuseppe Balsamo — known throughout Europe as Count Cagliostro — was imprisoned in the castle. His cell, on the Renaissance level, is still known by his name: la Cagliostra. Sentenced to life imprisonment, he was later transferred to the fortress of San Leo, where he died in 1795 without ever leaving Italy alive.
Cagliostro in the castle: full story → - 1798Modern
Napoleonic occupation
The revolutionary French army (1775–1799) forced the exile of Pope Pius VI and the surrender of the castle's garrison. The papal coats of arms on the fortress walls were chiselled off, the pontifical standard was replaced with the French tricolore, and the building was used as a French military barracks. The episode marked the first time in centuries that Castel Sant'Angelo flew a non-papal flag.
- 1870Modern
Annexation of Rome to the Italian state
With the unification of Italy and the dissolution of the Papal States, Castel Sant'Angelo ceased to be the fortress of the papal citadel and entered the new Italian national domain as a military barracks and prison. The transfer ended nearly five centuries of continuous papal possession, during which the castle had served as fortress, residence, treasury, and prison. It would never again belong to the Vatican.
- 1901–1915Modern
Conversion to the Museo Storico del Genio Militare
From 1901 onwards, the castle was opened to the public as the Historical Museum of the Italian Corps of Engineers. During the First World War, the castle also housed the artistic treasures evacuated from Italian war zones — a strategic role that recalled, on a smaller scale, the times when popes had used the same vaults to store the Vatican treasury during sieges.
- 1925Modern
Establishment of the National Museum
The royal decree of 1925 institutionalised Castel Sant'Angelo as the Museo Nazionale di Castel Sant'Angelo. Since then, the castle has remained continuously open to the public as a state museum, with progressive restorations restoring access to additional rooms, the Passetto di Borgo, and the upper terraces. It is today administered by the Direzione Musei Nazionali di Roma (dmnrm), under the Italian Ministry of Culture.
See these milestones in person
Most of the rooms involved in these milestones are part of the standard museum visit. The Sala Paolina (1545–47), the Cagliostra cell (1789), the prisons where Cellini was held (1538), the Stufetta of Julius II (1503–13), and the terrace where the Verschaffelt Angel still stands (1752) are all accessible to visitors. The Passetto di Borgo (1277) requires a specific guided tour.
Frequently asked questions
What is the official timeline of Castel Sant'Angelo?▾
How old is Castel Sant'Angelo?▾
When did the castle stop being a papal fortress?▾
What is the most important Renaissance episode in the castle's history?▾
Who built the angel statue on top of the castle?▾
What sources are used for this timeline?▾
Featured long-form stories from the timeline
- Ponte Sant'Angelo: 1,900 years of the Bridge of Angels →
- The Passetto di Borgo: secret papal escape route →
- The Sack of Rome 1527: when the castle saved the papacy →
- Benvenuto Cellini's escape from the castle →
- Beatrice Cenci: the noblewoman executed beside the castle in 1599 →
- Cagliostro: the alchemist imprisoned in the castle →
Sources and editorial method
The chronological skeleton of this page — the twenty-four milestones, their dating, and their order — is taken directly from the official brochure La Storia del Monumento published by the Direzione Musei Nazionali di Roma (Ministero della Cultura). Editorial expansion of each milestone draws on the Italian Ministry of Culture archives, CoopCulture interpretive materials, the Dizionario Biografico degli Italiani (Treccani), and the long-form pieces linked above. Where individual figures or episodes have their own dedicated Wikipedia entries cross-checked against scholarly sources, those have also been consulted. No content has been generated speculatively.
Edited by Gabriel — Google Local Guide Level 8, with on-site visits to Castel Sant'Angelo in 2025 and 2026.