Uninhabited until the first century AD, Emperor Caligula began the construction of a circus around 40 AD. The project was completed by Nero, named the Circus of Nero, and became the site of the first organized martyrs.
There is an ancient myth that Saint Peter, the Vatican's first Pope, was crucified upside-down at the circus of Nero.
Vatican City's first church, Constantinian basilica, was built in 326 over the tomb of Saint Peter, and triggered a population growth to the area. Then by the 5th century a palace was erected close by.
The Popes steadily governed and ruled over a large section of the Italian peninsula for over a thousand years until their territory was seized by the Kingdom of Italy in the mid 19th century.
To further add to the situation, Rome was annexed in 1870 and unified with the rest of Italy.
Although they were left undisturbed in their palace, the Popes refused to recognize the Italian ruling over Rome, and remained in the Vatican compound until a resolution was reached in 1929.
The Lateran Treaty resolved the dispute between the Vatican and Italy, and effective June 7, 1929 the Vatican was established as the independent State of the Vatican City.
During World War II, despite the German troops occupation of Rome, Vatican City remained neutral under Pope Pius XII.
In 1978 Pope John Paul II became the first non-Italian Pope since the Renaissance, and served for a little over 26 years - the second longest documented pontificate.
As one of the most acclaimed world leaders of the 20th century, Pope John Paul II was also the most traveled of all the Pope's, and visited 129 countries.
Following the death of Pope John Paul II, Pope Benedict XVI was appointed on April 25, 2005.
As the smallest state in the world, Vatican City includes Saint Peter's Basilica, the Vatican Palace (the Pope's formal residence), the Vatican Museum, the Sistine Chapel, and dozens of administrative buildings and historic monuments.