Complex sentence: Blausteinsee is located primarily the municipality of Eschweiler, the only exception being the Schlangengraben stream flowing to its north, which is part of the municipality of Aldenhoven.
Split into simpler sentences: Blausteinsee is located primarily the municipality of Eschweiler. The only exception is the Schlangengraben stream flowing to its north, which is part of the municipality of Aldenhoven.