Situated within the strictly protected core zone, the «Schratteflue» – the striking karst mountain in the biosphere – is one of Switzerland’s prime karst landscapes.

Karst is a type of terrain mainly made up of limestone. The Schratteflue range is made up of sediment from the ancient Tethys sea, deposited on the seabed and compressed into limestone. Thanks to the formation process, many fossilised shells and sea creatures can be found on the Schratteflue. The Schratteflue is also the type locality for the Schrattenkalk Formation, which means the rock was scientifically documented here for the first time. 

The appearance of a karst landscape like the Schratteflue was and is defined by water: it is shaped by rainfall, which causes the limestone to weather, and by underground streams that produced extensive cave systems. Its superficial ‘pavements’ feature highly intricate surface patterning, comprising razor-sharp rillenkarren (‘Schratten’), dolines (sinkholes) and much more. The plant life of a karst landscape depends on altitude: at lower levels, sparse coniferous forests alternate with moors and grasslands as the limestone is sealed with boulder clay and flysch. Exposed to the wind and weather, the limestone pavements above are almost completely devoid of vegetation.

Speleologists have been studying the extensive cave system of the Schratteflue since 1959. To date, they have discovered more than 250 caves with a total length of 40 km. At the very outset, they discovered the biggest cave: the Neuenburgerhöhle, which spans 15 km. With a height difference of 478 metres, the deepest cave is known as the Alpenschneehuhn system. The flow direction of the water trickling to the surface remained a mystery for a long time. In the course of a water tinting exercise in 1970, it was found that water coloured in cave P55 (in the middle of the Schratteflue) did not, as expected, reach the inlets of the Grosse Emme or Waldemme rivers, but travelled 20 km underground before emerging in Lake Thun 38 hours later. The cave explorers made other exciting discoveries, including three brown bear skeletons around 4,500 years old as well as moose antlers. In 1961, one explorer found a cave spider measuring just 2 mm in the Neuenburgerhöhle. It subsequently emerged that he had discovered a new, pre-ice age species that exists nowhere else on earth but the Schratteflue: the pseudoscorpion (pseudoblothrus thiebaudi). The caves of the Schratteflue also provide an important wintering site for bats. In 2022, a new type of bat for the canton of Lucerne was verified: the Alcathoe bat.