Today the Church celebrates the feast of the Dedication of the Lateran Basilica in Rome, the Mother Church of Catholicism. The Basilica of St. John Lateran is the cathedral of Rome. This is not St. Peter's, but it is the Pope's cathedral. Also called the Church of Holy Savior or the Church of St. John Baptist, it was the baptism church of ancient Rome. It was built in the time of Constantine and was consecrated by Pope Sylvester in 324. This feast became a universal celebration in honor of the basilica called "the mother and mistress of all churches of Rome and the world" (omnium urbis et orbis ecclesiarum mater et caput) as a sign of love for and union with the See of Peter.
The foundation of the Lateran Basilica goes back to the time of Constantine, the time of the last persecutions. The palace of the Laterani, on the Coelian Hill, belonged then to Constantine's wife Fausta. After his conversion, the Emperor gave it to the Pope as his private residence and founded in it the church of the Lateran. It was dedicated to Christ our Saviour by Pope St. Silvester on November 9, 324. In the twelfth century, it was given as its second title St. John the Baptist whose name was also that of the ancient baptistery connected with the church; hence the present name of the basilica, St. John Lateran. The first basilica having been destroyed, it was rebuilt in the tenth century by Sergius III and consecrated by Benedict XIII in 1726.
In the basilica and palace of the Lateran were held the Roman councils at which many were present at certain periods; five great ecumenical councils have also been held there. On the most solemn days of the liturgical year the station was at St. John Lateran. There sacred orders were conferred as well as the Easter baptisms. The residence of the Popes were there and the whole rhythm of Christian life made it the very center of Christianity for a long time.