* With 346 miles of cave passageways, this is the longest cave in the world. Some areas are still unexplored and uncharted.
* Native Americans first discovered entrances to Mammoth Cave about 4,000 years ago. They explored about 20 miles into the cave.
* The cave's Mammoth Dome is 192 feet high and the Bottomless Pit is 105 feet deep.
* During the War of 1812, black slaves mined saltpeter from cave sediments for use in manufacturing gunpowder.
* Public tours of Mammoth Cave began in 1816.
* Starting in the 1830s, slaves led tours through the cave.
* In the 1800s and early 1900s, weddings and performances were held inside the cave.
* The cave and the land above it were established as a national park in 1941.
* More than 2 million people visit Mammoth Cave National Park every year.
* Nearly 600,000 of those visitors take tours of the cave.
* Close to 4,000 people take tours of the cave every day during the peak season.
* Twelve species of eyeless, unpigmented cave dwellers live in Mammoth Cave.
* Three endangered species live in the cave: Kentucky cave shrimp, Indiana bats, and Grey bats.