Strengthened as of XIe century, the castle was built at the origin on a rock headland emerging from a marsh. The castle of Ferns, one of the principal keys of the duchy of Brittany, many times was besieged, ruined and rebuilt between XIe and XVe centuries. Also it offers a complete panorama of the military architecture, for the Romance time until constructions of triumphing artillery. With this architectural interest are added the richness of the historical and warlike memories, and the spectacular character due to the hugeness of the realization.