The area around the village of Crni Lug has many extreme relief depression points and is abyss abundant area. The area of Bijela Vodica is located on the tops of underground rocks below which underground watercourses are reported, flowing to the Bosiljevo. The ground under Crni Lug is constructed by numerous underground slopes and canals. Nearby Crni Lug is a limestone cave of Malenica, 15m long, 6m wide and 5m high. In this cave, there is a stream of Čimažev jarak. In the spring and winter, the water sprinkles so that the abyss cannot be devoured, and then enchants the surrounding area. In Malenica, on the west side, there are also two crampons which swallow water. Not far from this cave there is a sinkhole, and on the north side, there is another cave. In 1956 under the guidance of Mirko Maleza, the abyss of Malenica was explored. He announces his morphological and hydrological observations of the abyss and its surroundings, which mentions another active abyss. The first major speleological research began only in the late 60s and early 70s. Also, organized by the Commission for Speleology of the Croatian Mountaineering Association and SO PD Željezničar from Zagreb, on several occasions, from 1969 to 1976, investigated the abyss of the Vela Voda stream at Crni Lug. The research could have had a tragic outcome as at one point the group of speleologists, due to the appearance of an aquatic wave that prevented them from going to the surface, remained in the cave for three days. The watercourse of the Vela river and its tributary is constructed from impermeable rocks (sand and sandstone with sand and limestone) and after long periods of intense rainfall, a large amount of water can be drained in the short space of the abyss. The speleology group used a military telephone to communicate for help and the food packets were sent via stream which flows into the cave. The Vela Voda abyss is still the longest of the Risnjak massif. In this regard, according to the latest information from the Caving Speleology Commission of the Croatian Mountaineering Association on October 5, 2016, Vele Voda abyss has a horizontal length of 1495 m. Malenica is also great for rock climbing.