The Höwenegg volcanic complex with its mysterious lake is a jewel among the natural wonders of the Swabian Alb and protected as a reserve for rare plants and animals.
The volcano was active during the Neogene period about 10 million years ago. At that time, a crater lake formed, which was visited by numerous animals. Fossil finds of three-toed prehistoric horses, antelopes and rhinoceroses in the sediment of the lake prove the subtropical climate in this period.
There are a total of six outcrop sites. Volcanic rocks (basalt and basalt tuff) were mined here from about 1900 to 1980. In the former quarrying area, the present enchanting lake arose, which is therefore not a real "crater lake". It is part of the nature reserve and protected.
In this geological context, one distinction is important: The Höwenegg is part of the "Hegau volcanism". It does not belong to the "Swabian volcano" in the volcanic area around Urach.
The entire Hegau is designated as a National Geosite.