The Vatican is in Rome because it has been the religious and administrative center of the Catholic Church since early Christianity, traditionally founded by Saint Peter, who is considered the first bishop of Rome. The Vatican territory is located within Rome as an enclave because the popes historically ruled the Papal States around Rome for centuries, and after the Kingdom of Italy annexed Rome in 1870, the Lateran Treaty of 1929 established Vatican City as an independent sovereign state within the city of Rome to preserve the pope's spiritual and administrative independence. This location is also significant as Saint Peter's burial site near the Vatican Hill in Rome, making it the spiritual heart of the Catholic Church.