Holy See
Although the Holy See is sometimes metonymically referred to as the "Vatican", the Vatican City State was distinctively established with the Lateran Treaty (1929) between the Holy See and Italy to ensure the temporal, diplomatic, and spiritual independence of the Papacy. As such, ambassadors are officially accredited to the Holy See and not the Vatican City State. Conversely, Papal nuncios to states and international organisations are recognised as representing the Holy See and the integrity of the Catholic Church along with its 1.3 billion members, not the Vatican City State, as prescribed also in the Canon law of the Catholic Church (1983). The "Holy See" thus refers to the See of Rome viewed as the central government of the Catholic Church. The Catholic Church, in turn, is the largest non-government provider of education and health care in the world, while the diplomatic status of the Holy See facilitates the access of its vast international network of charities.
Vatican City
The name "Vatican" predates Christianity and comes from the Latin "", meaning Vatican Mount. The territory of Vatican City is part of the "Mons Vaticanus", and of the adjacent former Vatican Fields. It is in this territory that St. Peter's Basilica, the Apostolic Palace, the Sistine Chapel, and museums were built, along with various other buildings. The area was part of the Roman "rione" of Borgo until 1929. Being separated from the city, on the west bank of the river Tiber, the area was an outcrop of the city that was protected by being included within the walls of Leo IV (847–855), and later expanded by the current fortification walls, built under Paul III (1534–1549), Pius IV (1559–1565) and Urban VIII (1623–1644).
When the Lateran Treaty of 1929 that gave the state its form was being prepared, the boundaries of the proposed territory were influenced by the fact that much of it was all but enclosed by this loop. For some tracts of the frontier, there was no wall, but the line of certain buildings supplied part of the boundary, and for a small part of the frontier a modern wall was constructed.