Mammoth Cave National Park Kentucky Photo by John Hyun / Flickr (noncommercial use permitted with attribution/no derivative works).
Mammoth Cave National Park
The National Park Service preserves the cave system and part of the Green River valley and hilly country of south central Kentucky at Mammoth Cave National Park. Visitors experience vast chambers and labyrinths in the longest cave system known (more than 400 miles of the cave system has been explored).