Wolf's Lair was Adolf Hitler's first Eastern Front military headquarters in World War II, located in the Masurian woods about 8 km from the small East Prussian town of Rastenburg. 
Three security zones surrounded the central complex where the Führer's bunker was located. 
The complex, which would become one of several Führer Headquarters located in various parts of occupied Europe, was built for the start of Operation Barbarossa - the invasion of the Soviet Union - in 1941.