According to tradition the primitive church (8th century) that gave origin to the abbey of San Giovanni was built over the remains of a temple dedicated to Venus. The current construction is owed to abbot Oderisio II (1155-1204), who was buried in the sarcophagus walled into the main façade.
The most striking aspect of the building is chiefly the monumental prospect, with its great, ornate portal âof the Moonâ (13th century). Around the lintel of this door, four white marble slabs are sculpted with the story of St John the Baptist. The interior of the church has a abasilica layout, whit a nave and two aisles that terminate in apses.
The presbytery, raised above the level of the hall, is framed by a impressive triumphal depressed lancet arch. The altar, an ancient marble slab, is placed in the centre of the apse. Below the presbytery there is a crypt where interesting medieval frescoes cover the domes of the apses.
The visit concludes in the cloister which is formed by a gallery of twenty-nine triforium windows with sixty-eight plinth less mullions and coussinets decorated variously with phytomorphous and zoomorphous motifs.