The Holle is a river that flows from the city of Lutheria east to the river Kild. In Lutheria, a large source right under the city supplies fresh water to the river. Through a series of sluices, it flows down to the river Kild, where it meets at Hochter farm in Vöhren. The river is used for transportation, fishing, power, and recreation.   Close to the estuary, the river powers the Black Poplar Watermill in the Walden neighbourhood. This mill is used as a saw, oil, and flour mill and is one of the most important in the region.