Here's what you need to know about the Vatican, also known as the Holy See.
Facts: The full name of the country is the State of Vatican City, and it is the spiritual and governing center of the Roman Catholic Church.
It stands on Vatican Hill in northwestern Rome, Italy west of the Tiber River.
Tall stone walls surround most of Vatican City.
Historical documentation reveals that St. Peter was crucified at or near the Neronian Gardens on Vatican hill and buried at the foot of the hill directly under where the main altar of St. Peter's Basilica now stands. Excavations at the basilica between 1940 and 1957 located the tomb believed to be St. Peter's.
Vatican City has its own pharmacy, post office, telephone system and media outlets. The population is 839 (July 2013 est.).
The Vatican is an absolute monarchy. Full legislative, judicial and executive authority resides with the pope.
St. Peter's Basilica: It is the world's second-largest Christian church after the Yamoussoukro Basilica in Cote D'Ivoire. St. Peter's is not a cathedral, which is a bishop's principal church. The pope is the bishop of Rome, and his cathedral church is in Rome.
Built on the foundation of the first St. Peter's, the new basilica took 120 years to complete. Masonry, sculpture, painting and mosaic work continued for nearly another 200 years.
The dome of the basilica was designed by Michelangelo, and is 400 feet tall and 138 feet in diameter.
The church is shaped like a cross and is almost 700 feet long, 450 feet wide at its widest point, and stands on more than 18,000 square yards.
In the grottoes or necropolis, beneath the basilica, is a papal burial chamber. The tombs of many popes, including St. Peter (the first pope), are located here.
Vatican Palaces: The Vatican Palaces consist of several connected buildings with over 1,000 rooms. Within the palaces there are apartments, chapels, museums, meeting rooms and government offices.
The Palace of Sixtus V is the Pope's residence.
The Vatican museums, archive, library, gardens and other offices make up the remainder of the palaces.
The Sistine Chapel: A separate structure from the basilica, designed to be the pope's chapel, was commissioned by Pope Sixtus IV della Rovere.
The Sistine Chapel was designed by architect Giovanni dei Dolci. The decorations by Pier Matteo d'Amelia, Michelangelo, Raphael and others continued for sixty years after construction was completed.
It is the site of the papal conclave and where elections for the new pope are held.
It is one of the world's most famous galleries of biblical art with the ceiling by Michelangelo, tapestries by Rafael and Rosselli's Last Supper.
Timeline: 320's - Construction begins on the first St. Peter's, by order of Constantine the Great.
1473-1481 - The Sistine Chapel is constructed.
April 18, 1506 - Pope Nicholas V begins rebuilding and expanding St. Peter's Basilica.
1508-1512 - Michelangelo paints the ceiling of the Sistine Chapel.
February 11, 1929 - The signing of the Lateran Pacts between the Holy See and Italy establishes the Vatican City State, the smallest independent nation in the world, covering only 109 acres.
June 7, 1929 - The Treaty of the Lateran is ratified. Pope Pius XI gives up all claims to the Papal States, and Italy agrees to the establishment of the independent State of Vatican City.