Église St Jean, hewn out of the hillside's limestone rock from the 8C, is one of the greatest subterranean monolithic churches of Europe. It was probably designed to house the relics of the Saint Sepulchre, brought back from the First Crusade to Jerusalem (1096-99) by Pierre de Castillon, the lord of the castle at the time. Visit the moving necropolis before going up to the deambulatory, perched under the vaults at a height of 15m, for a splendid view of the entire church.