Located at the hearth of the national park with the same name and discovered in 1791, Mammoth Cave is the longest cave in the world. According to National Speleological Society (NSS), it measures a length of 405 miles or 651.8 km. The official name is actually Mammoth-Flint Range Cave System, coming from the ridge above the caverns.
Mammoth Cave National Park was designated in 1941, and some forty years later became a World Heritage Site. In 1990 was also classified as international Biosphere Reserve.
Despite its name, you shouldn't expect to find any mammoth fossils in the cave. The name only reflects the large size of some passages.