Papal Archbasilica of St. John Lateran is the cathedral church of the Dipcese of Rome and the official ecclesiastical seat of the Bishop of Rome, who is the Pope. It is the oldest and ranks first among the four Papal Basilicas of Rome having the cathedra of the Bishop of Rome. It claims the title of ecumenical mother church among Roman Catholics.
The Archbasilica stands over the remains of the 'new fort' of the imperial cavalry bodyguard. The fort was established by Septimus Severus in AD 193. Following the victory of Constantine I over Maxentius at the Battle of the Milvian Bridge, the guard was abolished and the fort demolished. Substantial remains of the fort lie directly beneath the nave. The remainder of the site was occupied by the palace of the Laterani family. This Lateran Palace came into the hands of the emperor when Constantine I married his second wife Fausta and it 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 Donatist schism. The palace basilica was converted and extended, becoming the residence of Poe Sulvester I eventually becoming the cathedral of Rome; the seat of the popes as bishops of Rome. It has been badly damaged twice by fire; in 1307 and 136, the damage adding to its decline. When the papacy returned to Rome it was considered unsuitable for the Pope’s residence and so after two moves the papal palace was built adjacent to St. Peter’s Basilica and the Papal court moved in there; it remains the papal residence today.
The Lateran Basilica houses 6 Papal tombs, a large number of the older tombs having been destroyed by the 14th Century fires. The last Pope to be entombed in the Lateran was Leo XIII.