Mammoth Cave National Park
Lying underneath a portion of west-central Kentucky is the vast Mammoth Cave. Along with connected caves to the east and west, the entire mapped complex constitutes the largest cave system in the world. The caves were formed by the dissolution of limestone by water, which also produced striking stalactite and stalagmite rock formations. The cave is inhabited by several unique animal species, including cave crickets, eyeless fish, and eyeless crayfish. A highlight of cave tours occurs when the lights are turned out, and visitors are momentarily plunged into total darkness and silence.