The castle of Conches-en-Ouches rises at the frontier of the duchy with the land of the powerful Tosny family.
It is characteristic of the military architecture of the Plantagenets at the end of the 12th century. Located in a dominant position on the edge of an escarpment, it consists of a circular tower, closely hemmed in by its enclosure on a partly man-made motte, detached from the plateau by wide ditches of c. 20 metres in width and ten metres deep.
The keep houses a noble hall with ogive vaulting. Stairs and corridors leading to the floors on floorboards are built into the thickness of the walls (2.60 m) which are also pierced by 6 narrow openings. There is a rising shaft within the thickness of the wall up to the grand hall. This is completely walled with limestones with a corbelled vault.
Flanking towers were added to the exterior wall in the period of Philippe Auguste (early 13th century). Another semi-circular tower, with a large bank to prevent undermining is a further subsequent addition (13th - 14th century).

Bibliography

- Decaëns, Joseph. “ Le château de Conches ”, L’architecture normande au moyen âge, actes du colloque de Cerisy-la-Salle, septembre 1994. - Caen : Presses de l'Université. Condé-sur-Noireau : Ch. Corlet, 1997, p. 323-324.
- Mesqui, Jean. Châteaux et enceintes de la France médiévale, de la défense à la résidence. - Paris : Picard, 1991.