Today, the Catholic Church celebrated a feast that I was not familiar with as an Anglican - the Dedication of St John Lateran, "mater et caput" of the Catholic Church.
The Lateran palace (once belonging to the Laterni family) was granted by Constantine the Great to Pope Miltiades sometime before AD 313. The palace basilica was converted and officially dedicated in AD 324 by Pope Sylvester I. At this time, the cathedra was placed inside and it officially became the Cathedral of Rome, dedicated Christo Salvatore, to Christ the Savior.
The Lateran Palace and Basilica have been rededicated two times. Pope Sergius III dedicated them to Saint John the Baptist in the 10th century in honor of its new baptistry of the Basilica. Pope Lucius II dedicated the Lateran Basilica to Saint John the Evangelist in the 12th century. It's full title is Archbasilica of the Most Holy Saviour and of Sts. John Baptist and John Evangelist in the Lateran.
The words Sacrosancta Lateranensis ecclesia omnium urbis et orbis ecclesiarum mater et caput are engraved in the main door, meaning "Most Holy Lateran Church, of all the churches in the city and the world, the mother and head."
Notable for Anglicans, Pope Leo XIII is buried there.