Ciboria are roofed structures with four or more columns built over an altar.

Dedicated to the Saviour and (certainly from the 7th century) to St John (both St. John Baptist and St. John the Evangelist) and known as S Giovanni in Laterano, the basilica is the cathedral church of Rome. It was regarded as the mother church of all Christendom, as is made clear by the inscription omnium urbis et orbis ecclesiarum mater et caput, which appears twice on the huge bases of the columns framing the central doorway to the present building. The church was probably begun after the Edict of Milan (313) and consecrated just before Constantine's departure to the East in 318; it would then have been incomplete and largely undecorated. The proportions and spatial distribution of the present nave (by Borromini,1646-1650) substantially reflect those of the Early Christian basilica. The main façade (1732-1736) by Alessandro Galilei is simple, solemn and harmonious, in a late Baroque Classicist style, with the benediction loggia on the main axis. Galilei also added the Corsini Chapel.