The Lateran Palace (; ), formally the Apostolic Palace of the Lateran (), is an ancient palace of the Roman Empire and later the main papal residence in southeast Rome. Located on St. John's Square in Lateran on the Caelian Hill, the palace is adjacent to the Archbasilica of Saint John Lateran, the cathedral church of Rome. From the fourth century, the palace was the principal residence of the popes, and continued so for about a thousand years until the Apostolic Residence ultimately moved to the Vatican. The palace is now used by the Vatican Historical Museum, which illustrates the history of the Papal States. The palace also houses the offices of the Vicariate of Rome, as well as the residential apartments of the Cardinal Vicar, the pope's delegate for the daily administration of the diocese. Until 1970, the palace was also home to the important collections of the Lateran Museum, now dispersed among other parts of the Vatican Museums. Following the Lateran Treaty of 1929, the palace and adjoining basilica are extraterritorial properties of the Holy See. History Pre-papal use The site on which the Basilica di San Giovanni in Laterano sits was occupied during the early Roman Empire by the domus of the Plautii Laterani family. The Laterani served as administrators for several emperors; their ancestor Lucius Sextius Lateranus is said to have been the first plebeian to attain the rank of consul, in 366 BC. One of the Laterani, Consul-designate Plautius Lateranus, became famous for being accused by Nero of conspiracy against the emperor. The accusation resulted in the confiscation and redistribution of his properties. Constantinian era The Domus Laterani came into the possession of the emperor when Constantine I married his second wife Fausta, sister of Maxentius. Around 312, Constantine had razed the imperial horse-guards barracks adjoining the palace, which was known as Domus Faustae or "House of Fausta" by this time; the equites singulares Augusti had supported Maxentius against Constantine. He commissioned the construction of the Basilica di San Giovanni in Laterano on the site. The Domus was eventually given to the Bishop of Rome by Constantine. The actual date of the gift is unknown but scholars believe it had to have been during the pontificate of Pope Miltiades, in time to host a synod of bishops in 313 that was convened to challenge the Donatists. Medieval Palace As Byzantium grew less able to help