This pond is located about 3 km north of Constance, near a hill called Purren (s. “Google map” below). The pond is located in a depression and is completely surrounded by forest. Therefore it has a high input of fallen leaves. It has a diameter of about 15 m. There is no inflow or outflow. In the layer of decomposing leaves there is a high concentration of bacteria, ciliates and rotifers. Algae and other groups are less represented.