Dor-lómin was a hollow land surrounded by mountains, and if it had any kind of river system, those rivers do not appear on any map. Nen Lalaith can hardly have been the only stream running out of the mountains into the land, but from the known geography, it is far from clear where those streams would have carried their water. This situation perhaps implies a central marsh or lake within Dor-lómin (like its neighbouring lands of Nevrast and Mithrim), but no such feature is recorded.