The Basilica of St. Antiochus Martyr, built over the Saint’s tomb, is one of the oldest monuments in the entire region. The first bishopric of the Sulcitan Iglesiente Diocese, it was erected around the fifth century, with a four-sided Greek cross plan, presbytery facing east and a probable domed body later revised and enriched with architectural elements. In the 12th cent. the church of St. Antiochus underwent extensions that changed its structure until the original early medieval building was unrecognizable. Attributable to this date are: the insertion of the side aisles and the lengthening of the nave, with the consequent abandonment of the Greek cross; the construction of the major apse and the chapel to the north; and a total covering of the walls with plaster and frescoes of little artistic significance, removed from the walls only in 1966. It is permissible that the Byzantine flooring, presumably mosaic, was ruined and then lost from the above century. The extension work did not end in 1100, but one has to reach the 18th cent. To see a further extension of the aisles and the creation of a facade in the late Baroque provincial style. After restoration work in ’66, a last considerable discovery inside the basilica consisted of the discovery of a square stone baptismal font and four sarcophagi, found devoid of any material, in a bay of the side aisle: an early study surmised the existence in the early Christian period of a baptisterial place outside the 5th-century Martyrium, which fell into disuse perhaps in Victorian times.