When you are halfway up the L 331 motorway that leads from Königswinter to Ittenbach you see the driveway to Mount Petersberg on your left side and a bus station on your right side. Some meters below the bus station a narrow path takes you into the woods to the Ofenkaulberg.
Since the end of the 18th century, (Tuffstein) was mined here, working below ground, for the production of ovens. Those from Königwinter were wellknown throughout the region. When the electric ovens came up, the business declined, and in the 30ies the mines in the Ofenkaulberg were given up.
During World War II, in 1945, a part of the armament industry was transferred into the Ofenkaulen mine. People from Russia, Poland and other countries were forced to work there. In February and March 1945 people from Königswinter sought shelter from air raids there. Today, the mine is close, because it is an important winter quarter for bats; many can hibernate here safe and in peace.