Kolkina Cave is the new the new deepest cave in Bulgaria studied until now, with 408,5m of displacement. This cave has been studied for more than 10 years.
The cave is located near the village Zimevitsa, Svoge Municipality, Sofia District. Its entrance is at 1285 meters altitude, near the crest of the Ponor Mountains, part of the Stara Planina.
The cave has several rivers, waterfalls, huge galleries and some extremely hard to reach areas. The researchers haven’t reached the cave’s end, and the expeditions continue to date. According to hydrological research the area has the potential to reach 800 meters displacement and galleries developments in length of 10 kilometers.