"By the close of the tenth century and the opening years of the eleventh, Foulques Nerra was raising castles throughout his own territories in Anjou, and on every available point of vantage he could wrest from his neighbour, the Count of Blois and Tours; the latter built fortresses to resist the aggressor and complete the network of strongholds begun by his father, Thibault the Trickster, one of the most turbulent nobles of his day."[67] [67] Anthyme St. Paul, _Histoire Monumentale de la France_. The keep of Langeais, on a precipitous hill overlooking the Loire, was founded by Foulques Nerra at the close of the tenth century; the walls, which are still standing on three sides, show traces of Gallo-Roman methods of construction; the dressed stones are of small size, and brick and stone are used conjointly for the voussoirs of the window arches. A large number of castles and keeps were built in the eleventh and twelfth centuries, among others those of Plessy, Grimoult, Le Pin, and La Pommeraye, the last on a mound surrounded by deep moats which separate three lines of circumvallation from each other; Beaugency-sur-Loire, the vast keep of which was four stories high; and Loches, which is ascribed to Foulques Nerra, but which seems to belong rather to the twelfth century, at which period military architecture had made a great advance. The keep of Loches is perhaps the finest of all such structures in France; in height it is nearly 100 feet; the ramparts seem to date from the thirteenth century; the form of the towers on plan is a pointed arch, a shape adopted as offering greater resistance at the part most frequently attacked by the sapper. [Illustration: 177. FALAISE CASTLE. KEEP] At Falaise, where the castle like that of Domfront is built on a rugged promontory, the ramparts are later than the keep, the architectural details of which point to the twelfth century. This hypothesis is supported by a passage in the Chronicle of Robert du Mont, quoted by M. de Caumont. In 1123 Henry II. rebuilt the keep and ramparts of Arques, and carried out similar restorations at Gisors, Falaise, Argentan, Exmes, Domfront, Amboise, and Vernon. [Illustration: 178. LAVARDIN CASTLE. KEEP] [Illustration: 179. KEEP OF AIGUES-MORTES. TOUR DE CONSTANCE]