Subalpine sinkhole
The largest sinkhole in Roška has a diameter of 160 m, a depth of 60 m, and a volume of 665 m³. It was formed by the collapse of the roof of a larger underground chamber. The bowl-shaped sinkhole retains some of its walls in the upper part. Below them is a steep slope covered with scree, and large rock blocks lie at the bottom. The slope is dominated by deciduous trees (ash, maple), while the bottom and shady parts of the slope feature a frost-tolerant spruce forest that has been preserved from the last ice age. The cold air at the bottom is trapped due to a temperature inversion and the influx of cold air from underground cracks in the collapsed rocks. Koliševka is protected as a natural monument and has been excluded from forestry management as a forest reserve. It is left to develop naturally, so be sure to observe it only from the edge!