Veryovkina Cave, the deepest known cave on Earth, plunges a staggering 7,257 feet (2,212 meters) into the abyss, forming a vast, vertical chasm that ... and determined explorers have dared to ...

Two explorers venture into the Seti Gorge of the Himalayas, a chasm so narrow and deep that none have descended into it, while research exposes the geological origins of the gorge.