The famous Wimsen Cave, also called Friedrichshöhle, is the only show cave in Germany that can be entered by boat. The water cave is the source of the river Zwiefalter Ach and explored up to one thousand metres.
It has 1,260 metres in length. However, visitors can enter the cave by boat only on a distance of 70 meteres, as the water level then reaches the cave ceiling. Such submerged parts in a cave are called siphons in speleology.
Water caves may have dry areas and also areas partially or completely filled with water. This depends on the current water level. Where areas are filled with water, erosion of rocks still takes place. The Wimsen Cave is therefore a still active cave. Its age is estimated to be over a million years.
From time to time, researchers go on the dangerous diving tour into the cave. In the "treasure chamber" at the rear area of the cave, ceramics and human bones have been found. They are still discussed among experts. Examinations of one bone revealed that it dates back to the Bronze Age. At that time, this part of the cave was still dry.