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ull of stones, which he tore apart and scattered all around Kras. Karst phenomena The karst world holds many mysteries. This land never fully reveals its underground beauty, and only the bravest can take a peek into its unseen wonders: hollows, caves, funnel-shaped holes, periodic waters, disappearing and reappearing rivers and intermittent lakes such as Cerknica Lake. The majority of the karst area (over two-thirds) consists of limestone; others are of dolomite, conglomerate, calcarenite, and breccia. The formation of karst caves is very complicated; they take over ten thousand years to develop. Water and limestone form beautifully shaped stalactites and stalagmites, sometimes united into pillars, curtains and draperies, baldachins, sinter (the sediment made from springs) pools, and club-shaped stalactites-made of malgonite or the so-called "cave milk." Among the most interesting karst phenomena is Snezna Jama (Snow Cave) in the northwestern slope of Raduha mountain. It is the highest elevated tourist cave in Slovenia. Along with the huge amounts of ice and sinter ornaments, which can only be found at such heights, there are also sinter formations that are at least twenty times as old as in any of the known karst caves. Karst species The main characteristic of the area is its varied landscape and climate conditions, which are directly reflected in the variety of its flora and fauna. Karst caves are home to numerous species of bats. Postojna Cave is inhabited by a rare animal, "human fish" or proteus (picture above), living only in its underground rivers. The constantly changing Karst world along with human activities made important natural habitats disappear. Yet new ones have emerged, and this has changed the natural composition of the Karst flora. In recent decades around ten types of nesting birds, typical of Karst pastures, have completely disappeared. The number of birds of prey has, it seems, increased. Also due to the rapid overgrowth of the meadows, a rapid decrease in the number of vipers has been recorded. A remarkable and rich variety of insects, especially butterflies, are becoming more and more endangered. Special care for nature is needed in these vulnerable areas. Exploration With approximately 7000 underground caves are already researched and around 1000 are yet to be catalogued, there is still much work left for speleologists, people who study caves. Considering extensive exploration during the last two centuries, Slovenian words-such as jama, dolina, polje, and ponor-have been adopted internationally in speleology. The typical feature of a polje (field or small valley) are the ponors, swallow holes where the water leaves the valley. The internationally accepted term used in karstology for a steep-sided and flat-floored depression-doline or dolina (valley )-owes its origins to the dolina in the Skocjan area (Velika and Mala dolina) as part of Skocjanske jame (Skocjan Caves). Taking great interest into research of our rich subterranean world isn't surprising or new. Janez Vojkard Valvasor, a Slovenian historian from 17th century, mentioned 70 caves in his famous book 'Slava vojvodine Kranjske' (Glory of the Duchy of Carniola). Speleology in Slovenia has a long tradition as one of the country's most beautiful caves, Vilenica, was opened for sightseeing in the 17th century and it had probably the first guided tour ever. The deepest caves reach 1300 metres in depth and extend several kilometres. The most famous caves among tourists are definitely the Postojnska jama and Skocjanske jame, both renowned for their beauty. Skocjanske jame have been listed in UNESCO's World Natural and Cultural Heritage List since 1986.