CASTLE OF SANT'ANGELO. — In Rome, on the right bank of the Tiber, opposite the Campus Martius, Hadrian had a new mausoleum built for the imperial family, since that of Augustus was already filled with tombs. Construction began around AD 130 and was completed by Antoninus Pius in 139. The mausoleum consisted of two parts: an inner cylindrical body (diameter 64 m, height 21 m) and
Castel Sant'ANGELO — St. Ursula and the bride meet with Pope Ciriaco. In the background, C. S. A. in its 15th-century form.
Painting by Carpaccio (1490–1513) — Venice, Gallerie dell'Accademia.
an outer large square plinth (length 89 m, height 15 m), connected by a series of walls arranged in a radial pattern. From the tumulus rose a high podium supporting, it seems, the quadriga of the Sun or a colossal statue of the emperor. Modern studies (G. Lugli, *I monumenti antichi*, III, Rome 1938, p. 707) consider unfounded the 16th-century hypothesis, still accepted in the last century, that the final crowning was a pinecone. Access to the central structure was, as today, through a vestibule preceded by a corridor. Above the burial chamber was another square room, and above that a very high circular room. Perhaps there was a fourth room at the top, within the podium.
After housing the remains of emperors up to Caracalla, under Honorius (395) the mausoleum began to form part of the defenses of the Urbs. The fortification works consisted mainly in the construction of a high wall connecting the structure to the right bank of the river; this wall was defended by 6 towers, 163 merlons, 13 windows for ballistae, and 18 for archers.
Modern archaeologists disagree on the reconstruction of these fortification works. According to Lanciani (*Forma Urbis*, Rome 1893–1901, tavv. VII and XIV), there was a large projection on the front with 6 towers; Richmond (*The City Wall of Imperial Rome*, Oxford 1930, fig. 6), however, reconstructs only two towers at the end of the bridge and two parallel walls between the bridge itself and the entrance to the mausoleum. This reconstruction, though, excludes 4 of the 6 towers mentioned in the regional catalogs. The new defensive function of the mausoleum was tested by the first barbarian descent: that of the Goths under Alaric (410). It then withstood the assaults of the Goths under Vitiges (537), of Narses, and of Totila (548).
Probably in the 10th century the structure was transformed into a castle by Alberic and Marozia; from then on the monument played a major role in the history of Rome and the papacy. At this time it witnessed the murders of Popes John X (928) and Benedict VI (974), and the imprisonment of John XIV (985). Later it became the property of the Crescentii (still called *Castellum Crescentii* in the *Mirabilia* of 1100 and 1200). But already by the 12th century the monument began to take on its current name of C. S. A., documenting the cult of the Archangel; a cult first expressed by a chapel at the top of the structure, later replaced by a statue of the Archangel. Popular tradition links this cult to the story that in 590, following the prayers of St. Gregory, who invoked an end to a terrible plague, an angel appeared on top of the mausoleum, sheathing his sword as a sign of the granted divine grace.
In 1277 the Castle passed into the power of the papacy, of which it became the stronghold, and was connected to the Vatican by the *passetto* or "Borgo corridor," built by Nicholas III.
An important restoration in 1389–1404 under Boniface IX (by Niccolò di Pietro Lamberti of Arezzo) earned the Castle the epithet "wonderful structure," as reported in the Jubilee chronicles of 1400; it was carried out to repair the extensive damage caused by the people after the victory of Urban VI over the antipope Clement VII (1379).
This was followed by works under Martin V (1417–31) and Eugenius IV (1431–47), and then the very significant works of Nicholas V (1447–55). He had two small chapels built at the entrance to the Pons Aelius; in the mausoleum he added three small towers at the corners of the base and reinforced the central tower and the Roman wall of the quadrilateral base; on top of the "maschio" (i.e., the central tower) he placed a statue of the Archangel Gabriel, in memory of the ancient miraculous apparition.
Even more notable were the works carried out by Antonio da Sangallo the Elder (drawings in the Vatican and the Escorial in Madrid) for Alexander VI (1492–1503): a tower was built in front of the entrance; a perimeter moat was dug, fed by water from the Tiber; the central cylindrical body was raised; the tower above (called "dei Crescenzi") was rebuilt after being struck by lightning in 1497; the towers of Nicholas V were reinforced with an octagonal base and their battlements restored; within the Castle were created storerooms (the *oliare* and *silos*) and a large cistern. After these works, the Castle became a very well-fortified stronghold, defended by 200 gun emplacements. These fundamental changes to the Castle are documented by various views: a detail from a fresco by Bicci di Lorenzo (cloister of S. Bernardo, Arezzo) showing the structure before Nicholas V’s works; a detail from Mantegna’s decoration in the *Camera degli Sposi* in the Palazzo di Mantova takes account of Nicholas V’s works; a medal was struck to commemorate Alexander VI’s works. Another notable depiction of the Castle at the end of the 15th century is in Carpaccio’s painting showing the meeting of St. Ursula and her bridegroom with Pope Ciriaco.
During the pontificate of Julius II (1503–13), work on C. S. A. was directed mainly toward embellishment: toward the bridge, the loggia attributed to Antonio da Sangallo the Elder was opened. This was followed by Leo X (1513–21), who built on the level of the courtyard of honor the chapel dedicated to the Medici saints Cosmas and Damian, perhaps executed from a design by Michelangelo, and began the construction of a bath.
Clement VII (1523–34) continued this work, having the environment and two ground-floor rooms decorated. Giulio Romano and Giovanni da Udine worked on them. Clement himself was besieged there in 1527 during the Sack of Rome, an event that ended in surrender and flight. Cellini, who was present, described some scenes of that memorable event. He returned there as a prisoner under Paul III, who had an apartment built there consisting of: the Room of Apollo, the Pauline Hall, the Room of Perseus, that of Cupid and Psyche, the corridor between the two aforementioned rooms, the Adrianeum Room, the Room of Garlands, the Cagliostra (so called because it is said to have hosted Cagliostro at the end of the 18th century), the cabinet of the Dauphin and the Salamander, and that of the Stork (so called from the depiction of the emblems of Paul III). At this time the statue of the Archangel struck by lightning was also replaced with a marble angel by Guglielmo della Porta. Moreover, as part of the strengthening of Rome’s defenses in view of the Turkish and Barbary threat, Paul III gave great importance
The consolidation of the Castle. The works studied by Michelangelo, Antonio da Sangallo, Bartolomeo de' Rocchi, were not, however, carried out.
A third external pentagonal wall was built under Paul IV (1555-59) by Camillo and Latino Orsini, but in a completely provisional manner (documented in 1557 by the plans of Rome by Paciotto and the Beatrizet), to resist the invasion of the troops of the Duke of Alba in the service of Spain, which had entered into war against the Pope; the wall was destroyed by a flood (14 Sept. 1557); following its layout, Pius IV in 1561 had a new masonry wall built by Francesco Laparelli da Cortona, Latino Orsini, Galeazzo Alessi, and other military architects. Under Paul IV the Castle also had its entrance gate, a work by Salvestro Peruzzi (1556). Demolished in 1892 for the works on the Lungotevere, it was rebuilt in 1933, between the bastions of St. John and St. Luke.
The fortification work of Pius IV was continued, between the Castle and the Borgo, by Pius V (1566-72). He extended the outer moat as far as the Tiber and near the river erected a half-bastion which was later called that of St. Spirit.
Other important works were carried out under Urban VIII, between 1626-30, with the architects Vincenzo della Greca, Gian Battista Mola and, later, also Bernini. The most important works consisted in having built in the bastions casemates, galleries and emergency gates; raised barracks, warehouses and powder magazines between the second and third walls; enlarged and reinforced the bastions of Alexander VI, which from then on were distinguished by the names of the Evangelists; the bastions of the pentagonal wall were named: of the Saviour, of St. Mary, of St. Paul, of St. Peter, of St. Spirit.
After Urban VIII, the access bridge was instead arranged, by Bernini, under Clement IX (1667). The Castle, having lost its character as a fortress, was destined only to barracks and prison.
Benedict XIV (1740-58) had the angel of della Porta replaced with the bronze one, which is still there today, by P. Verschaffelt.
Under Pius IX (1865) the bastion of St. Spirit was demolished. In 1870 the Castle remained a barracks; however, in 1886, at the instigation of Mariano Borgatti, to whose care the monument was entrusted, excavations and restoration works were undertaken which lasted for forty years, thus resuming the previous excavations of 1825 which had brought to light the helical ramp and the burial chamber; as a national monument, the Castle became the seat of a military museum.
In 1934, on a design by A. Spaccarelli, the isolation of the structure was carried out, which partly at least regained its sixteenth-century appearance. — See Pl. LVII.