Vietnam's Son Doong cave, which is 200 meters high and over 1.5 kilometers long, was certified as the world's largest cave in 2010. The British team that originally discovered the cave has returned for their third exploration accompanied by an NHK crew. In this eight-day exploration, the crew lights up the interior of the "Great Hall" for the first time revealing the hidden world of the cave. This program examines the mysteries behind how such a giant cave was formed.
