Documentary
TV Show
National Geographic: The Worlds Biggest Cave
Ended1 seasons1 episodes~60 minUnited StatesEnglishNational Geographic
This week, Gray Line Halong Cruise would like to introduce the national geographic world biggest cave - Phong Nha Ke Bang, Quang Binh, Vietnam. Researchers have discovered 39 caves located deeply in Phong Nha, Ke Bang. Some of the caves still are mystery.