Caves | Planet Earth Ep. 4

This episode explores “Planet Earth’s final frontier“: caves. At a depth of 400 metres (1,300 ft), Mexico’s Cave of Swallows is Earth’s deepest Pit Cave freefall drop, allowing entry by BASE jumpers. Its volume could contain New York City’s Empire State Building. In this episode divers explore the otherworldly cenotes of the Yucatán Peninsula, appearing to be flying in water (because it is so clear), allowing viewers a glimpse of the hundreds of kilometers of caves which have already been mapped. The Waitomo Caves with the Arachnocampa luminosa is also shown. Also featured is Borneo’s Deer Cave and Gomantong Cave. Inhabitants of the former include three million wrinkle-lipped free-tailed bat, which have deposited guano on to an enormous mound. In Gomantong Cave, guano is many metres high and is blanketed with hundreds of thousands of cockroaches and other invertebrates...