The Crisbecq Battery, also called Marcouf Battery, was a World War II artillery battery constructed by the Todt Organization near the French village of Saint-Marcouf in the department of Manche in the north-east of Cotentin peninsula in Normandy. It formed a part of Germany's Atlantic Wall coastal fortifications. The main armament were three Czech 21 cm Kanone 39 canons, two of which housed in heavily fortified casemates up to 10 feet thick of concrete. The Battery, with a range of 27–33 kilometers, could cover the beaches between Saint-Vaast-la-Hougue and Pointe du Hoc.
Prior to the Invasion of Normandy, the battery was subject to frequent aerial bombardments but it was still operational on D-Day, 6 June 1944. On 6 June 1944, at 5 a.m. the commandeur of the crisbecq battery was the first to sight the Allied invasion fleet through the battery rangefinder.
Wikipedia https://en.wikipedia.org/wiki/Crisbecq_Battery
Coordinates 49°28'43.374" N -1°17'43.009" E