National Parks Traveler Episode 129: Exploring Mammoth Cave National Park
Mammoth Cave National Park in Kentucky is a World Heritage Site and International Biosphere Reserve. It was designated a national park in 1926 and fully established and opened in 1941 -- 80 years ago. At 412 miles, the cave itself is nearly twice as long as any other known cave system. Geologists believe there may even be a couple more hundred miles of undiscovered passageways.