The World's Biggest Cave

In 2009, a team of British cavers investigated a recently uncovered cave in a remote Vietnamese jungle. The Son Doong cave is enormous; can it be larger than the current world-record holder? The explorers traveled for miles through the cave before hitting a 46-foot-high wall. Now, follow the team as they return to Son Doong to finish exploring the cave and climb the wall. Will Son Doong prove to be the worlds biggest cave? And what secrets are undiscovered inside this unique ecosystem?

A half-mile block of 40-story buildings could fit inside this lit stretch of Hang Son Doong, which may be the world?s biggest subterranean passage.

Like a castle on a knoll, a rock formation shines beneath a skylight in Hang Son Doong. A storm had just filled the pool, signaling that exploring season was coming to an end.

Navigating an algae-skinned maze, expedition organizers Deb and Howard Limbert lead the way across a sculpted cavescape in Hang Son Doong. Ribs form as calcite-rich water overflows pools.