If you walk a little way further up, you will see a geological feature which is a major exception in the Volcanic Eifel.
The Windsborn cinder cone is the only volcanic crater north of the Alps which is filled with water. And not only that: Because of its particular location, it provides a habitat for extremely rare plants. Unlike other bodies of water, the crater lake on top of the volcano is not fed by groundwater, which would be enriched with minerals from the ground. Instead it relies on precipitation for the supply of water and nutrients. The lake is therefore very short of nutrients and also lacks oxygen. Although at first sight this might be a disadvantage, the situation is a paradise for particular plants. Bogbean loves the margins of the lake, and its white flowers make a fine show when they are in full bloom in May/June.
Marsh cinquefoil, which has red flowers, comes into bloom a little later in June/July. Together with sphagnum mosses, the bogbean and marsh cinquefoil form - with their adventitious roots - a wide carpet, which stretches from the bank out over the surface of the lake. In the course of time, the crater lake will become silted up and turn into a raised bog.
Our tip: You can explore the whole of the Mosenberg Crater Row on a three-kilometre circular walk. Along the path, display boards of the Manderscheid Geo Route provide more information.