National Geographic Worlds Biggest Cave (2010)
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?