West facade from north, 11th century. The facade is imposing and austere, with thick walls and arrow-slit windows indicating its double purpose as a fortress. The only decoration comes from tall recesses beneath Lombard bands (small blind arches) and a cross cut in the top center. The north tower dates from the late 12th century. The portal is an incongruous 19th-century addition, as is the walkway between the west towers.