The Passetto is the underground street Vatican hidden under the walls of San Pietro. A gallery of almost 300 meters, hiked, leading to Castel San'Angelo.
This gallery is located in the north of St. Peter beneath the high walls 10 meters parallel to Bernini's colonnade, its construction dates back to the sixth century when the king of the Ostrogoths built the first walls to surround the territory Vatican.
Only in 1377 when the popes returned to Rome to establish the residence of St. Peter's Basilica was thought of a road linking their residence at the Castle. Nicholas III, who was the first Pope moved to Rome thought of restoring the walls of the Vatican already in a bad state and for the occasion he built an underground passage from the Vatican would lead directly to Castel San'Angelo to take refuge in case of danger.
After two centuries were some changes by subsequent popes, it was transformed into a gallery of Alexander VI who put his signature affixing the emblem of his papacy, visible even today on a postal Vatican at the end of Passetto.
When the boundaries were widened Vatican was built a wall parallel to the Passetto and were opened many steps to create a network of underground roads that allowed connections.
The access door to the Passetto is covered by Bernini's colonnade and is located between two towers, this gate in time assumed different names. Initially called Porta Veridaria because introduced the Vatican Gardens, Port of Nibbi because once abandoned became the nest of birds of prey and Port of the Swiss because it is located behind the barracks of the Swiss guard.
After being closed for a long time, the Passetto was reopened with the Jubilee of 2000 after being renovated and made safe today can be visited.