The Vatican

Vatican City is the world's smallest fully independent nation-state (at just over 108 acres, and with fewer than 1,000 residents).

Before there was a Vatican, there was a hill in ancient Rome known as Mons Vaticanus (Vatican Hill). No one knows what "Vaticanus" meant, though it might have been a word drawn from the ancient Etruscan language. Back then, the Vatican was something of a low-rent district. It was the home of a few farmers and potters, while Rome proper sprawled across a series of hills a short distance away.

That changed when people started burying their dead on Mons Vaticanus. The burial ground was popular among early Christians, and tradition says the apostle Peter was buried there after he was executed around AD 64. Roughly 250 years later, when the emperor Constantine converted to Christianity, he honored his new faith by erecting a basilica over Peter's reputed grave. (That building was torn down in the 15th century, so the present St. Peter's could be built.)

The new basilica brought a steady stream of pilgrims to Rome to pray at Peter's grave--and to spend money while they were there. Merchants set up shop on the Vatican to exploit the tourist trade, priests came to minister to the pilgrims, and, eventually, foreign heads of state built palaces to stay in when they visited Rome.

As the Vatican expanded, so did the church's temporal authority. In 754, Pope Stephen II traveled to France to anoint the Frankish king Pippin III (Charlemagne's father). In return, Pippin helped the pope establish dominion over a large chunk of central Italy, which became known as the Papal States. For more than 1,000 years, the Papal States existed as a sovereign territory, with popes for a "king."

The capital of the Papal States was not the Vatican, but Rome itself--of which the Vatican was a part until the 19th century. During the early Papal States years, popes didn't even live in the Vatican. They resided across town in the Lateran Palace, which was reportedly given to the pope by Constantine himself.

That changed in 1377, when the papacy returned to Rome after spending 68 years in Avignon, France. Pope Gregory XI found the Lateran Palace had fallen into disrepair, and rather than renovate that building he took up residence in the Vatican Apostolic Palace. Later, Pope Sixtus IV had a chapel built inside the palace for the pope's own use. It's known as the Sistine Chapel, after "Sixtus."

Over the centuries, the size of the Papal States waxed and waned. Then, in the 19th century, a movement for Italian unification and independence took off. (Prior to then, Italy was not a unified nation.) The Papal States, which divided Italy in two, clearly stood in the movement's way. The church tried to hold on, but by 1870 everything but the Vatican had been annexed by the new kingdom of Italy.

In response, Pope Pius IX declared himself a "prisoner of the Vatican" and never again set foot outside its walls. Finally, in 1929, the Vatican and Italy formalized their relations. The two signed a treaty in which the church recognized the Italian government, and Italy recognized the Vatican as a sovereign state. So it remains today.

Mark Diller