Under the German system of "Naturräume", Stadtallendorf lies in the West Hesse Depression zone ("westhessische Senkenzone") which is divided into basins and ridges. With respect to these, the town lies on the Upper Hesse Ridge which separates the Amöneburg Basin in the west from the "Schwalmbecken" (another basin) in the east. On this ridge may also be found the Neustadt Saddle, abutted by the town's northeast edge. This upland is part of the divide between the Rhine and Weser watersheds.