Does 'It has served as a fortress for the Gallo-Romans, the Visigoths, Franks, and medieval French (you can see the layers of their masonry in the ramparts).' provide a contradiction to the established premise 'The fortress was built by the medieval French in 1173.'
It has served as a fortress for the Gallo-Romans, the Visigoths, Franks, and medieval French (you can see the layers of their masonry in the ramparts).###The fortress was built by the medieval French in 1173.