This major monument is known for its ancient two-level crypt. According to legend, the bones of the legendary Ste-Anne, mother of the Virgin Mary, were miraculously discovered in this crypt in the 8th century, resulting in the building of the cathedral. Her life is depicted in a beautiful set of 14th-century stained-glass windows at the end of the apse. Her shroud is also displayed among the reliquaries of the treasury. Scholars speculate that Anne was not the biblical figure, but a dim memory of the primeval Pan-European mother goddess sometimes known as Ana or Anna Perenna to the Romans.
In the 13th century, the present church was enlarged, and in the 18th century the floor was raised and the broken-barrel vault turned into a higher arched vault. The oldest part of the cathedral is the tower crypt, which still has both a funerary monument honoring a priest in the time of Apia Julia and Carolingian flagstones. The church and treasury are filled with rare ecclesiastical artifacts. In the chapel of St. John the Baptist is an early Christian marble sarcophagus from the Pyrenees. Among the treasures in the sacristy are 11th- and 12th-century manuscripts, elaborate vestments, and an 11th-century Arab standard brought back from the First Crusade. The nave is adorned with scenes from the life of Christ, painted by Pierre and Christophe Delpech in the 18th century.