Standing between the Tiber and the Vatican, this circular and medieval "castle" has long been one of Rome's most distinctive landmarks. Opera-lovers know it well as the setting for the final scene of Puccini's Tosca; at the opera's end, the tempestuous diva throws herself from the rampart on the upper terrace. In fact, the structure began life many centuries before as a mausoleum for the emperor Hadrian. Started in AD 135, it was completed by the emperor's successor, Antoninus Pius, about five years later. It initially consisted of a great square base topped by a marble-clad cylinder on which was planted a ring of cypress trees. Above them towered a gigantic statue of Hadrian. From the mid-6th century the building became a fortress, a place of refuge for popes during wars and sieges. Its name dates from 590, when Pope Gregory the Great, during a procession to plead for the end of a plague, saw an angel standing on the summit of the castle, sheathing his sword. Taking this as a
sign that the plague was at an end, the pope built a small chapel at the top, placing a statue next to it to celebrate his vision—thus the name, Castel Sant'Angelo.
Enter the building through the original Roman door of Hadrian's tomb. From here, you pass through a courtyard enclosed in the base of the classical monument. You enter a vaulted brick corridor that hints at grim punishments in dank cells. On the right, a spiral ramp leads up to the chamber in which Hadrian's ashes were kept. Where the ramp ends, the Borgia pope Alexander VI's staircase begins. Part of it consisted of a wooden drawbridge, which could isolate the upper part of the castle completely. The staircase ends at the Cortile dell'Angelo, a courtyard that has become the resting place of neatly piled stone cannonballs as well as the marble angel that stood above the castle. (It was replaced by a bronze sculpture in 1753.) In the rooms off the Cortile dell'Angelo, look for the Cappella di Papa Leone X (Chapel of Pope Leo X), with a facade by Michelangelo.
In the courtyard named for Pope Alexander VI, a wellhead bears the Borgia coat of arms. The courtyard is surrounded by gloomy cells and huge storerooms that could hold great quantities of oil and grain in case of siege. Benvenuto Cellini, the rowdy 16th-century Florentine goldsmith, sculptor, and boastful autobiographer, spent some time in Castel Sant'Angelo's foul prisons; so did Giordano Bruno, a heretical monk who was later burned at the stake in Campo de' Fiori, and Beatrice Cenci, accused of patricide and incest and executed just across Ponte Sant'Angelo.
Take the stairs at the far end of the courtyard to the open terrace for a view of the Passetto, the fortified corridor connecting Castel Sant'Angelo with the Vatican, which recently featured in the book and 2009 film Angels and Demons (it's possible to request a visit; call for more information). Pope Clement VII used the Passetto to make his way safely to the castle during the Sack of Rome in 1527. Near here is a caffè for refreshments. Continue your walk along the perimeter of the tower and climb the few stairs to the appartamento papale (papal apartment). As if times of crisis were no object, the Sala Paolina (Pauline Room), the first you enter, was decorated in the 16th century by Pierino del Vaga and assistants with lavish frescoes of scenes from the Old Testament and the lives of St. Paul and Alexander the Great. Look for the trompe l'oeil door with a figure climbing the stairs. From another false door, a black-clad figure peers into the room. This is believed to be a portrait of an illegitimate son of the powerful Orsini family. Out on the upper terrace, at the feet of the bronze angel, take in a magnificent view of the city below.