What actually are sinkholes?

Numerous dry valleys connect the Altmühltal with the overlying, plateaus. Formerly the plateaus were called “the cisterns-country”, because of its clay soils. The residents had almost only rainwater , available in wells.

The reason for this:
The many fortified rainwater trickles away quickly in the slightly soluble, calcareous layers of the Jura. In the underground, there are forming caves and fissures. On the surface, for example between Göhren and Bieswang , by leaching the limestone, there are striking widely visible funnel or lowering soil – the so-called sinkholes.