Lechuguilla

At 150.4 miles, Lechuguilla Cave is the eighth-longest explored cave in the world and the second deepest in the continental United States. It is most famous for its unusual geology, rare formations, and pristine condition.
  • Location: Eddy County, New Mexico, U.S.
  • Nearest city: Carlsbad
  • Length: 138.3 mi (222.6 km)
  • Governing body: National Park Service
Data from: en.wikipedia.org