Clouds billowing out from the entrance of the cave and the sounds of a raging river caught the attention of Ho Khanh, a local man who was searching for shelter from a storm in the Phong Nha-Ke Bang National Park while foraging for food and timber to earn a modest income in 1990, according to Oxalis Adventure, a local tour company that leads expeditions in the area.
Little did Khanh know that he had just discovered an opening in a limestone cliff that led to the planet’s largest cave, which is so big that it has its own weather system along with underground rainforests, never-before-seen animals and rock formations called stalagmites the size of tall buildings.