Hirschzungen sinkhole in Hainholz

The Hirschzungen sinkhole has steep and partially overhanging walls. Its age is estimated at around 500 years. The collapse of the underlying karst cave took place in historical times.
The deer tongue is a fern that needs shady and moist steep slopes on limestone or gypsum soil. These requirements are very well met in the approximately 10 m deep sinkhole,

The deer tongue is a fern with a simple leaf and is considered rare. She loves soaked rock walls and subsoil with little soil. The northernmost deposit known to me is in front of Smoo Cave in northern Scotland. There is also a small stock growing in a column in the Roman Forum. There are several deposits in the gypsum karst area of the southern Harz.

With the surrounding vertical walls, this is a prime example of a sinkhole. Here is also the most impressive stag-tongue fern occurrence in the region that I know of. Sporadic occurrences occur again and again along the karst hiking trail, but they are not as noticeable as here in the sinkhole. Deer tongue fern is under nature protection.