There are many things that make the Son Doong Cave in Vietnam a remarkable natural wonder; at about 9km in length, 200m in width and 150m in height, it is the largest cave in the world, with caverns capable of fitting entire city streets and skyscrapers. It is home to a river, jungles, and entire cave ecosystems. Only slightly less remarkable is the fact that, until 2009, we did not even know how grandiose and impressive Son Doong (or Mountain River) Cave really is. The Son Doong Cave in Vietnam was recognized as the world's largest cave in 2010. The program presents amazing images from deep inside the cave filmed for the first time using high-definition cameras.