To the north, the Wiehen descends to the North German Plain into a region known as the Lübbecke Loessland. On the banks of the Weser, opposite Porta Westfalica, lies the Wesergebirge, which is the eastern continuation of the Wiehen Hills. This ridge is of similar geological construction and runs as far as the area of Hessisch Oldendorf to the Süntel hills. Southeast of the Wiehen Hills are the Lippe Uplands, to the south the Ravensberg Hills, to the southwest in the area of the Tecklenburg Land are the northern foothills of the Teutoburg Forest, and to the northwest are the hills of the Gehn and the Ankum Heights, the Damme Hills and the Stemweder Berg. North of the northwestern tip of the Wiehen liest the great bog of the Großes Moor.