Built early in the 11th century on the site of a former castle, the abbey is a fascinating site. Now in ruins, there are a number of buildings to see, the most evocative being the cathedral which is classified a national monument for its mix of Romanesque, Gothic and Renaissance architecture. Other buildings are an octagonal-shaped kitchen, refectory, dormitory and chapter house built around a central garden as well as cellars, turrets and ramparts.