The Langer See is a lake situated in the south-eastern outskirts of Berlin, the capital city of Germany. The lake is aligned south-east to north-west and forms part of the course of the River Dahme. The Langer See is approximately 11 kilometres (6.8 mi) long, with an average width of 221 metres (725 ft) and an area of 2.43 square kilometres (0.94 sq mi).