Over the south portal, which is not in the transept but next to it in the nave, is an elaborate tympanum carved with biblical scenes and retaining some of its original paint.

Formerly a collegiate church, in the Port quarter of Clermont-Ferrand. From the 10th century to the French Revolution it was served by a community of canons, regular until the 13th century, and thereafter secular. The basilica is one of the five Romanesque churches in Auvergne known as the "greater" churches (majeures). According to tradition, the church was founded by the bishop of Clermont, Saint Avitus, in the 6th century and was rebuilt in the 11th or 12th centuries after being burned down by the Normans. The apse and chevet are richly decorated with mosaics and carving. The capitals, which are among the finest in Auvergne, principally depict scenes from the Bible, but also some from the Psychomachia of Prudentius.