Mittelwerk was a German World War II factory built underground in the Kohnstein to avoid Allied bombing. It used slave labor from the Mittelbau-Dora concentration camp to produce V-2 ballistic missiles, V-1 flying bombs, and other weapons.

Mittelbau-Dora was a Nazi concentration camp located near Nordhausen in Thuringia, Germany. It was established in late summer 1943 as a subcamp of Buchenwald concentration camp, supplying slave labour from many Eastern countries occupied by Germany, for extending the nearby tunnels in the Kohnstein and for manufacturing the V-2 rocket and the V-1 flying bomb. In the summer of 1944, Mittelbau became an independent concentration camp with numerous subcamps of its own. In 1945, most of the surviving inmates were sent on death marches or crammed in trains of box-cars by the SS. On 11 April 1945, US troops freed the remaining prisoners.