The Biggetalsperre is one of the largest dams in Germany and is the second largest in North Rhine-Westphalia in terms of storage volume. It is located in the center of the Ebbegebirge nature park between the towns of Attendorn in the north and Olpe in the south. Since 1965 it has been damming the left tributary of the Lenne to the Biggesee with a dam in order to control the flow of water in the Lenne and the Ruhr in terms of volume and to increase flood protection. The operator and owner of the dam, also known as Bigge for short, is the Ruhrverband based in Essen, which operates a total of seven other dams in the Sauerland. As a special feature, the formerly independent Listertalsperre was integrated as a fore basin during construction.