The Arnsberg Forest Nature Park lies between the river Möhne in the north, on which the Möhne Reservoir is located, and the deep valley of the Ruhr in the south. Between these two valleys the park is situated between Möhnesee in the northwest, Rüthen in the northeast, Brilon in the east, Olsberg in the southeast, Meschede in the south and Arnsberg in the southwest; Warstein lies within the nature reserve. To the north is the heavily forested region of the Haarstrang, to the east are the Brilon Heights, to the south is the Rothaargebirge, to the southwest is the Lennegebirge and to the west the terrain gradually descends towards Dortmund into the Ruhr.