Château-Gannes is one of the circular enclosures that were very common through Europe. The defensive system was restricted to a wooden palissade on an earth mound surrounded by ditches. The strongest point was a gate tower in stone of which there are remains of the lower floor, dating from the beginning of the 12th century, and which enabled access through the wall into its courtyard enclosure.
- Les châteaux normands de Guillaume le Conquérant à Richard Cur de Lion. - Caen : Musée de Normandie, 1987. - p. 22-23