The Doggerstollen (also called Doggerwerk) is a tunnel system in the Houbirg mountain range. The tunnels of the Doggerwerk were forced laborers from 1944 to 1945 from the Hersbruck satellite camp. War-essential BMW aircraft engines were to be manufactured in the planned underground production facility. The site management and SS management staff were located in Happurg. The completed total length is 3.9 km, today there are still 2.6 km of it. The camouflage name was "Esche 1". It has been planned to make parts of the public accessible for some time.
The Hersbruck concentration camp was built in July 1944. It was used exclusively for the prisoners who had to work in the "Doggerwerk" near Happurg, 5 kilometers from Hersbruck. An underground factory for BMW aircraft engines with a total area of 120,000 square meters was to be built. Eight linked tunnels with a total length of 3.5 kilometers were driven into the mountain.