The relics of the two Marks, who are said to have been buried at Saintes-Maries, are bestowed in the upper storey of the apse of the fortress-church, a remarkable building of the 12th century with crenelated and machicolated walls.
A strong machicolated and turreted wall surrounds the rock, running along its base on the south, ascending halfway up the cliff on the north, on which side it stands close to the abbey wall, and again descending on the west.
The walls, which are of great strength, are surmounted by machicolated battlements, flanked at intervals by thirty-nine massive towers and pierced by several gateways, three of which date from the 14th century.
