The Windsborn cinder cone near Bettenfeld is part of the Mosenberg volcano group and is the fourth eruption site looking from SE. It is separated from the other eruption sites by a distinct depression and rises about 50 m above the Devonian basal complex. Today its crater holds a lake with an accretion zone, surrounded by a ring ridge of slag agglomerate. These were ejected redhot from the volcano and fused together during cooling. Particularities Windsborn is the only crater lake in the Eifel and north of the Alps which is permanently filled with water. It is only fed by rainfall. The lake water has a yellowish tint and at a pH-level of 5-6 is slightly acidic. Scientifically, it’s considered a dystrophic lake. The lake today has a quaking bog-bog bean-marsh cinquefoil belt and slowly silts up from the outside in.