National Geographic Documentaries

Mysteries Underground (27x1)

Air date: Nov 18, 1992

Chronicles the exploration of the world's most exotic new cave: New Mexico's Lechuguilla Cave, which remained undisturbed for millions of years until 1986. Also see the 1972 expedition that stumbled upon a passageway that linked the Mammoth and Flint Ridge Cave systems, creating the longest cave network in the world.