Wieliczka Salt Mine is one of the oldest deposits of rock-salt in Europe. It was mined during the XIIIth-XXth centuries. The Mine shows the development of methods and technologies of salt mining for seven centuries. The underground corridors and galleries of the museum (combined with a health resort) are located on the seven underground levels (57-198 m depth). The total length of the underground passages is more than 200 km. In 1978 the Mine was added to the list of UNESCO World Heritage Sites. Nowadays the Mine is used as a museum and as a health resort for those who have respiratory disorders.