Lateran Palace (c-350). 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. 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. Constantine I and the bishops of Rome 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. As Byzantium grew less able to help prevent Lombard incursions, the papacy became more independent of the Empire. Prior to the early eighth century, the residence of the bishops of Rome was not called a palace, but rather the Lateran patriarchate. The incentive to refurbish the Lateran patriarchate as a true palace was to create an imperial residence from which the pope could exercise not only spiritual but also temporal authority. The pope's palace at the Lateran in Rome was extensively added to in the late eighth century by Pope Hadrian I and Pope Leo III, who built an enormous triclinium. It was one of the most famous halls of the ancient palace and was the state banqueting hall, lined with mosaics. Nothing remains of this, but in 1743 copies of the mosaics were made from drawings and placed in a specially built structure opposite the palace. The existing structure is not ancient, but a representation of the original mosaics is preserved in a three-part mosaic: In the centre Christ gives their mission to the Apostles; on the left he gives the keys to St. Peter and the Labarum to Constantine; while on the right St. Peter gives the stole to Leo III and the standard to Charlemagne, an image meant to represent the Frankish king's duty to protect the Church. The triclinium and the sala del concilio, an oblong hall with apse mosaic and five ornate niches on each side, were built around 800 to serve as the heart of papal ceremonial. Architecturally they were reminiscent of Byzantine imperial buildings in Constantinople. In the tenth century Sergius III restored the palace after a disastrous fire, and later it was greatly embellished by Innocent III. This was the period of its greatest magnificence, when Dante speaks of it as beyond all human achievements. At this time the centre of the piazza was occupied by the palace and tower of the Annibaldi family. Between this palace and the Lateran basilica was the equestrian statue of Marcus Aurelius, which at the time was erroneously believed to represent the Christian Emperor Constantine. A copy of the equestrian statue is now placed in the centre of the Capitoline Square while the original has been safely preserved for display in the Capitoline Museums. In its place, the Lateran obelisk was erected.