It has long been known that during the late third and early fourth centuries A.D. over 80 previously unfortified towns of Gaul were surrounded by new defences. These can be distinguished from those of the twenty-five ancient cities fortified in the previous centuries by the thickness and height of their walls, by the number of their projecting towers, and by the fact that their foundations were in nearly every case constructed from re-used blocks, tombstones, and architectural fragments coming from earlier buildings. Although at several places such walls survived almost intact until the nineteenth century, having formed the principal defences of towns such as Bordeaux, Dax, and Sens throughout the Middle Ages, the best preserved example still remaining is at Le Mans (Sarthe), the capital of the province of Maine. There can be seen more complete and more easily accessible specimens of features existing in poorer condition at Beauvais, Carcassonne, Jublains, Périgueux, Senlis, Tours, and other towns. A full description of the walls of Le Mans will serve to illustrate the characteristics of the late Roman fortifications of a medium-sized Gallic city.