Largest Cave in The World, With It's own Whether System.

Hang Son Doong, located in Phong Nha-Ke Bang National Park, Vietnam, is the world's largest natural cave. It was discovered in 1991 by a local man named Hồ Khanh and later explored by the British Cave Research Association in 2009. The cave is over 5 kilometers long, 200 meters high, and 150 meters wide, with a volume of 38.5 million cubic meters, making it the largest known cave passage in the world by volume. The cave is open to visitors, but access is strictly controlled and limited to 1000 a year, with all tours organized and led exclusively by Oxalis Adventure Tours. Visits are restricted to the months between the end of January and the end of August due to the rainy season, after which the cave becomes largely inaccessible.