In 1912 a detonation at the gypsum mine near Hinterbrühl went awry, the lower gallery and shafts of the mine became completely flooded, creating the largest subterranean lake in Europe. Roughly 60 meters below ground level, the “Big Lake” has a surface of 6,200 square meters and needs to be drained of replenishing groundwater on a daily basis. Even though the explosion led to the closure of the mine during World War II, German aircraft were built in the dry, upper levels of the former mine, the production being protected from Allied bombing in its vast tunnel system.
