In the autumn of 1943, the Germans began experimenting with a new high-tech weapon named V3. In short it was a high-pressure pump capable of firing multiple arrow-shaped projectiles towards (in theory) a given target. Tests were carried out at a facility outside Stettin in the current north-west of Poland. Construction of a real facility began inside a mountain in Mimoyecques, about 15 kilometres southwest of Calais in northeastern France. The idea was to bomb London with V3 projectiles, but Britain had recieved information about it and destroyed it before it could be put into action.

However, at the end of November 1944, the Germans managed to quickly build a new simplier facility consisting of two high-pressure pumps on a slope outside Lampaden in western Germany. The first pump was put into service in December of the same year and the second pump in early January 1945. A total of 183 projectiles were fired, of which 142 were fired at the city of Luxembourg, just over fourty kilometres from Lampaden. Other projectiles were fired at targets during the German Ardennes offensive. The accuracy was virtually zero and it did not cause any major material damage. Because of its minimal impact on the war, it also did not have any symbolic value as a weapon of retaliation. 

Current status: Demolished (2022).

Location: 49°38' 19.76" N 06°42' 59.77" E

Get there: Car.

My comment:

There is really nothing left of the facility worth visiting. A small concrete slab at the second high-pressure pump and small openings for bats and similar animals in sealed entrance to what was once storage rooms. That was all I could find when I visited the site. If one looks carefully one can distinguish where the high pressure pumps have been located. Unfortunality there is not even a small information board on the site.

Follow up in books: Irons, Roy: Hitler´s Terror Weapons: The Price of Vengeance (2013).