The Lateran Palace (Latin: Palatium Lateranese) is an ancient Roman palace located on the Caelian Hill, one of the seven original hills of Rome. From the 4th century AD, the palace served as the primary residence of the Pope—the highest-ranking office of the Roman Catholic Church—for roughly a millennium until ultimately the Papal seat of power was transferred to the Vatican. In modern times, the Lateran was retained as a papal palace in the Vatican Papal State, the sovereign territory of the Holy See.