The Lateran Complex
The Lateran complex includes several places of great interest: the Basilica with its Cloister, the Baptistery and the Scala Santa which contains inside the Papal Chapel of the Sancta Sanctorum.
The Archbasilica of SS. Salvatore e dei Santi Giovanni Battista ed Evangelista, more commonly known as St. John Lateran, is the oldest church in the West.
Commissioned by Emperor Constantine after his conversion and victory over Maxentius, it was consecrated in 324 AD. And this is why it is defined as the mater et caput of all the churches of Rome and of the world.
This basilica is the cathedral of the diocese of Rome and the seat of the Bishop of Rome, the Pope.