The Earth's large, deep calcareous caves are virtually inaccessible and therefore barely explored - requiring expert diving where flooded. Some of its wildlife is as strange and specific as in the deep, darkest part of the ocean, whether physically adapted -notably to the dark. Nevertheless, some caves(did) play an important part in native cultures, even as sources of fresh water for some Mayan cities. Written by
Did You Know?
First humans featured on the show. See more
David Attenborough - Narrator
This is our planet's final frontier, and a world where only the most adventurous dare to go.
[BASE jumper disappears into black hole
Featured in Zomergasten: Episode #24.1
Planet Earth Theme
Written by George Fenton
Performed by BBC Concert Orchestra See more