The Wild Lake is one of the most fascinating karst springs in Slovenia as it is both a spring as well as a lake and cave, all in one. It is situated in the beginning of the Strug gorge, under the cliff-like slopes of the Črni Vrh Plateau, which represents the larger part of the spring’s background area. The majestic, almost 100 m high slopes are made of Lower Cretacious limestones (with an age of 145–100 million years) on an impermeable basis of Paleocene-Eocene flysch rocks (66–34 million years), the youngest rocks in the Idrija region.
The water flows into the lake from a steeply descending underwater cave tunnel. So far, divers have explored it to the depth of 164 m, which is the edge of human capability. In dry periods, the water forms a small lake at the base of the imposing cliffside. During heaving rainfall, however, the lake spews forth an enormous amount of water, forming a mushroom-like shape up to several tens of centimeters in height.
The steep cliffsides are home to alpine flora such as the Carniolan primrose (Primula carniolica), a species endemic to Slovenia. In the lake’s syphon, divers have encountered the olm (Proteus anguinus).