The Vatican City, the world's smallest independent state, has a rich and ancient history. Founded on the site of the martyrdom of Saint Peter in the 4th century, it became the center of the papacy and the Roman Catholic Church. After being part of the Papal States, it became a sovereign state in 1929 through the Lateran Treaty with Italy. Since then, it has been a major spiritual, administrative, and artistic center, welcoming millions of pilgrims and housing artistic treasures such as the Sistine Chapel and St. Peter's Basilica.