The cave is a part of hydrological system with waters entering underground between the sinkholes of the Studený potok and its tributaries in small valleys of Volariská and Múčnica and waters flowing out to the surface by the Brestovská Spring. It was formed in the Mesozoic limestone-dolomite formation (Ramsau dolomites with positions of limestone of Gutenstein type), mostly along the tectonic faults. Development of upper parts was predetermined by lithological boundary between Mesozoic carbonate rocks and conglomerates from the Late Tertiary. Underground passages were modelled during Middle and Late Quaternary by ponor water course, now flowing through cave lower parts. The cave spreads in south-eastern direction as far as the Volariská Valley. Water stream in the cave leads through several siphons overcome by cave divers. We can distinguish two cave levels. Cave length is 1,890 m (the eastern part is behind the inflow siphon). Calcite decoration is mostly represented by soda straw and carrot stalactites. Flowstone films and deposits including smaller rimstone pools can be found in the upper drier parts of the cave. Fragile, eccentric microcrystal forms of aragonite were also discovered here. The average annual air temperature in the Entrance Hall is 4.9 °C and in the rear parts 5.4 °C. Important fauna habitats in the cave are bound mostly to underground waters. Crustaceans Diacyclops languidoides (Copepoda), Niphargus tatrensis (Amphipoda) and Bathynella natans (Syncarida) are typical representatives of relict aquatic cave fauna of the Tatra Mts. The most important terrestrial forms of arthropods are isopod Mesoniscus graniger and harvestman Ischyropsalis manicata, which are Carpathians endemites. Springtail Protaphorura janosik is an endemic troglobite of the Western Carpathians, glacial relict inhabiting mostly cold caves. Nine bat species were described from entrance parts of the Brestovská Cave. The most common is the greater mouse-eared bat (Myotis myotis), occasionally occurs also the greater horseshoe bat (Rhinolophus ferrumequinum) having here one of the most northern hibernation places in Slovakia as well as in Europe. History Since time immemorial, the Brestovská Cave attracted attention of adventurers and treasure seekers. Underground secrets of the Zuberecká Valley fascinated also the Polish botanist and Tatra naturalist T. Chalubinski, who mentions the “cave at Cold Water springs” (today’s Brestovská Cave) for the first time in literature in 1866. J. G. Pawlikowski took interest in the cave in the half of the 80ies of the 19th century and as early as then he was thinking of opening the cave to tourists. The cave was surveyed by capt. Kopečný with a group of soldiers from the Dolný Kubín garrison during 1923 – 1925 within the framework of the Club of the Czechoslovak Tourists. J. Brodňanský, collaborating with F. Čejka and others joined the survey after establishment of the Slovak Speleological Society in 1949. The first speleo-diving effort was made in 1968. The divers J. Kucharovič and V. Sláčik overcame the inflow siphon and disovered new parts of the cave in 1979. They were later measured by Z. Hochmuth, J. Kucharovič, P. Marek and V. Sláčik in 1981. By now seven siphons are known in the underground river.