Caen, capital of western Normandy

After the battle of Val-ès-Dunes, Duke William needed to assert his power more firmly in the western part of the Duchy and use a fortified town as a base. His choice was Caen which was still no more than an emerging centre of population to which Richard II had granted certain privileges. Acts promulgated by William's ancestors, Richard II and Richard III, indicate a large rural domain (villa), vineyards, meadows, windmills and also churches and a port, but as yet no urban structure.

William had founded a church in Caen, Sainte-Paix (1061), in honour of the Council held there after his victory at Val-ès-Dunes (1047). He gave the town its true birth, however, by building a great castle there on which work began in c. 1050.

The foundation of two abbeys confirmed the new importance that the Duke wished to give the town. They also reinforced the marriage vows of William and Matilda in exchange for the lifting of the interdict on their marriage. The work on the Abbaye aux Dames, a foundation of Matilda's began in 1059; and the work on the Abbaye aux Hommes, William's foundation began in 1065.

The ducal town, at the foot of the castle, and the two abbey towns were the kernels around which Caen was to develop. From the time of William, a palace complex was erected in the castle to receive the Duke and his itinerant court. The political and administrative functions, extended by his successors, sustained the development of the town, which was well located at the crossroads of the Duchy and whose port was to benefit from the conquest of England.

Based in Rouen and Caen, William from this point onwards had a firm grip on the entire Duchy.