Vatican City is located close to the right banks of the Tiber River, on a small hill that covers part of the Montes Vaticani (Vatican Hill) of the ancient days, upon which a few villas had been built in the days before Jesus’ birth.

Roman Emperor Caligula (37-41 A.D.) had a private circus built there, in which, there is reason to believe, many of Rome’s Christians were martyred during the rule of Nero (54-68). They were also killed in the adjacent gardens.

North of the circus, in a necropolis located along a secondary road, is the burial place of Saint Peter, in which Emperor Constantine built a grand basilica between 324 and 326, which was replaced by the current one, built in the 16th to 17th century.

The State’s territory, which covers a surface area of 0.44 km2 (44 hectares), is partly surrounded by walls and includes Saint Peter’s Square up to the marble strip that joins the ground to the outer parts of the Colonnade, and marks the confines of the State to the boundaries of the Square, a boundary that can however, be freely accessed. Even though it is part Vatican City’s territory, by regulation, it is subject to supervision by the Italian Republic’s police authorities.

There are five entrances into the State, protected by the Pontifical Swiss Guard and by the Gendarmerie Corps of Vatican City. Access into the Vatican Museums is from Viale Vaticano, not far from Piazza del Risorgimento.

Due to the size limitations of Vatican City’s territory, many of the Holy See’s Bodies and offices are located in properties inside the city of Rome (especially the buildings in Piazza Pio XII, on Via della Conciliazione, Piazza San Calisto, Piazza dell Cancelleria and Piazza di Spagna).

In accordance with the Lateran Treaty, these properties are protected under the same immunity enjoyed by diplomatic agents of foreign states under International Law (Embassies). The areas in which the properties are located are commonly referred to as extraterritorial areas.