Baradla cave

The Baradla Domica cave system in Hungary is one of the longest researched, visited for centuries for its speleothems. As part of the Aggtelek Karst, the cave system extends more than 25.5 km and includes the 5.3 km Domica cave. The cave has a natural entrance at Aggtelek, at the foot of a high white cliff that overlooks the edge of the village. It has an articulated, meandering main channel 7 km long, with a rock tunnel, on average, 10 m wide and 7 to 8 m high with a few giant caverns. The main branch has several short and long connecting side branches. A significant part of the cave has varied colors and shapes providing an unparalleled spectacle of decorative stalactites. Subterranean river waters run through the main branch at times of flood. Natural entrances to the cave have been open from ancient times, and there are traces of Neolithic occupation.

Wikipedia