The Passetto

As you navigate Rome—whether by car or on foot—you may find yourself crossing streets and squares that, at first glance, seem to lack historical or artistic significance. Near Piazza Pia, one such road passes beneath a series of ancient-looking arches that many, at a glance, mistakenly assume to be remnants of a Roman aqueduct.

In reality, these arches belong to the Passetto di Borgo, a hidden passage connecting Vatican City to Castel Sant’Angelo. This discreet yet strategic corridor has been the setting of dramatic historical events, including escapes, sieges, and pivotal moments in Rome’s past. Known affectionately by Romans as “Er Coridore”, walking through the Passetto di Borgo is like stepping back in time, retracing the footsteps of popes and prisoners, all while enjoying breathtaking views of ancient and modern Rome as a backdrop to this extraordinary architectural marvel.

The Passetto di Borgo at Castel Sant’Angelo: What to See

The Passetto di Borgo, also known as the Passetto di Castel Sant’Angelo, is an elevated corridor that links the Bastione San Marco, embedded within the perimeter walls of Hadrian’s Mausoleum, to the Vatican, specifically the Apostolic Palace.

The earliest traces of this structure, in its most primitive form, date back to 547 AD as part of the defensive system surrounding the military camp of Totila, the king of the Ostrogoths.

Today, the Passetto di Borgo stands as an 800-meter-long fortified passage, featuring both an open panoramic section and a covered passageway. The narrowest part measures only 75 cm wide, allowing just one person at a time to pass through.

This corridor is actually the last remaining section of the Leonine Walls, built in the 9th century under Pope Leo IV to protect the Civitas Leonina and, most importantly, St. Peter’s Basilica from Saracen raids.

A few years later, during the renovation of the Vatican walls, an additional covered passage was added to the Passetto. The primary purpose of this addition was to provide a secret escape route for the pope in times of danger, allowing them to flee from the Vatican to Castel Sant’Angelo, which had by then been transformed from Hadrian’s Mausoleum into an almost impenetrable fortress.

However, the Passetto di Borgo was not only used as a papal escape route. It also served as a hidden passage for transferring prisoners to Hadrian’s Mausoleum, especially when secrecy was required. Few people know that the historical dungeons of Castel Sant’Angelo once held famous figures such as:

Count Cagliostro, the infamous alchemist and occultist
Benvenuto Cellini, the renowned goldsmith and sculptor
Giordano Bruno, the philosopher condemned for heresy
Beyond its role as an escape and prisoner transfer route, the Passetto also played a strategic military function. It allowed defenders to launch arrows from above onto enemy forces attacking the Borgo district, with special openings built along the walkway for this purpose.

There is some debate regarding the true architect of the Passetto. Some attribute its construction to Pope Nicholas III, who is credited with moving the papal residence from the Lateran Palace to the Vatican.

Restorations and Historical Events

Over the centuries, the Passetto di Borgo underwent several restorations, notably during the pontificates of Nicholas V, Sixtus IV, and Alexander VI in the 16th century.

In 1562, under Pope Pius IV, several new arches (fornici) were built in various locations, including:

Vicolo del Campanile
Vicolo del Farinone
Via del Mascherino
Vicolo delle Palline (named after the Medici emblem of Pius IV, engraved on Porta Angelica)
Via Porta Castello, which is separated from the new monumental gate by the Madonna della Misericordia (1953)
Vicolo d’Orfeo in Borgo Pio, where visitors can admire a beautiful 18th-century “Madonnella”, a wooden shrine topped with a triangular pediment
The final section of the Passetto di Borgo consists of eight large arches, stretching over the lush gardens of Parco Adriano, leading to the Bastione di San Marco. Along with three other corner towers, this bastion marks the Marcia Ronda, the fortified walkway surrounding Castel Sant’Angelo.

The Passetto’s Role in Historic Escapes and Sieges

A guided tour of the Passetto di Borgo reveals some of the most dramatic historical events that took place within its walls, including:

The Escape of Pope Alexander VI Borgia (1494): During the French invasion led by King Charles VIII, Alexander VI fled through the Passetto to take refuge in Castel Sant’Angelo.
The Sack of Rome (1527): One of the most infamous events in Rome’s history, this brutal attack saw Landsknecht mercenaries under Emperor Charles V lay siege to the city. Pope Clement VII, realizing he was in grave danger, fled through the Passetto.
According to legend, Clement VII was shielded by a black cloak, held over him by courtiers and nobles, in an attempt to conceal his white papal robes. He barely managed to reach Castel Sant’Angelo, narrowly dodging bullets fired by the German mercenaries—traces of these gunshots can still be seen on the Passetto’s walls today.

The Swiss Guard, however, was not as fortunate. In a heroic but tragic act, most of its members were slaughtered while trying to protect St. Peter’s Basilica.

A Unique Experience in Rome’s Hidden History
Visiting the Passetto di Borgo is a once-in-a-lifetime journey into the secrets of Rome’s past. This seemingly unremarkable structure conceals centuries of history, from papal intrigue and military strategy to dramatic escapes and fierce battles.

Today, the Passetto remains one of the most fascinating and overlooked sites in Rome, offering a rare chance to walk the same path as popes, prisoners, and defenders of the Eternal City.