The reservoir is about long and has an average width of . It begins near the point where the Lenne flows into the Ruhr, and ends with the weir and hydroelectric plant of Hengsteysee. The Klusenberg, a hill that is part of the Ardey range, is located just north of the Hengsteysee. There is also a pumped-storage plant on this reservoir, named Koepchenwerk after Arthur Koepchen.