The Dümmer is located in the Dümmer depression. One and a half miles to the west, the Damme Hills begin to rise, eventually reaching a height of 145 m. Around the lake are fens (Niedermoore) and raised bogs (Hochmoore). The lake lies in the Dümmer Nature Park, which is just under 500 km² in area, and in which the Damme Hills and Stemweder Berg form the central elements of the landscape.