Mysteries Underground (1992)

Closet spelunkers, don your helmet flashlights and rejoice! Mysteries Underground from National Geographic is your personal tour guide of the vast worlds that exist right under your feet. Venture across both time and space, from the failed 1925 attempt to rescue caving legend Floyd Collins from Kentucky's Sand Cave to a claustrophobic retelling of 1972's pioneering Flint Ridge-Mammoth Cave connection to the 1986 discovery of New Mexico's 60-mile-long, 1600-feet-deep Lechuguilla. Plummet far into the inky blackness that is the world of caving, where explorer's footprints endure as if they were made on the moon, and where the surroundings seem just as alien. Witness the treacherous beauty of underground ice formations. Learn about the intricate cave food chain based on nitrogen-rich bat guano. Spy ancient cave paintings, eyeless fish, and albino salamanders. It's a thrilling hour you won't forget. It's also bound to make wherever you live seem a lot larger and brighter than you previously thought.