Huda luknja Gorge

At the northeastern edge of the Šalek valley, where the Paka River cuts through the limestone mass between Tisnik and Pečovnik, Huda luknja Gorge is concealed in the narrowest part of the ravine. It is accessible from the main road from Velenje to Slovenj Gradec.

Tisnik is threaded by about 1.6 km of open shafts and underground caves with an extremly complex underground environment. Tisnik has the greatest number of underground phenomena per square kilometre of any karst area in Slovenia. In times past cave-dwelling bears sought shelter in these caves.

Huda luknja Gorge is botanically highly interesting because of its unique location and ecological conditions. Some plants which usually are found in sub-mediteranean biogeographical zones grow here, as do plants which are normally characteristic of alpine regions and are remnants from the Ice Age. Alpine bells (Cortusa matthioli), an endemic species, grow an inaccessible cliff behind the entrance to Huda luknja, and are found nowhere else in Slovenia with the exception of Uršlja gora.

Some organisms have adapted to the extreme environments found in caves. The spider Troglophyphantes diabolicus was first found in Huda luknja. The barely visible, two-millimetre large beetle Aphaobiella tisnicensis, which got its name from Tisnik, is also a curiosity. The Ponikva River is home to the transparent, flattened crustacean Niphargus scopicauda. Piles of dropping also indicate the presence of bats.

Huda luknja Cave is the present path of the flow of the Ponikva River through Tisnik. Investigations of the cave have uncovered some fragments of crockery, bones and antique coins. The cave was first opened to tourists in 1895, last opened in 1995, and guided tours are possible.