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. The cave is named for the canyon through which it is entered, which is named for Agave lechuguilla, a species of plant found there. Lechuguilla is in Carlsbad Caverns National Park, New Mexico, United States.