Cayeux-sur-Mer is a small town located on the southern side of the Baie de Somme and stands between two long beach areas.
Along both flanks of the town, protecting the entrance to the river Somme, are half a dozen defensive strongpoints. There are further sites inland of the coast, including a large radar station.
The strongpoints were commanded from this central location from a R610 battle headquarters bunker which can be found nestled amongst beachside properties in the centre of town.
It is flanked by two R501 type single group shelters for personnel, the only other remaining buildings from a site which once also featured three R600 emplacements for 5cm KwK anti-tank guns which have since been covered or removed from the beach front area.