An unmissable stop on the Compostela pilgrim route, the abbey was founded by Charlemagne to house a relic of the True Cross. The 11C tower soars above the shrine, inside which the high altar stands directly above the crypt where the relics were displayed. The chapter house has good 13C carving from the central portal of the abbey façade. The treasury contains a fine collection of Romanesque croziers and Gothic goldwork.