Son Doong Caves in Vietnam is one of the most beautiful natural caves and the largest ever found in the world. Hang Son Doong cave complex of Phong Nha - Ke Bang National park, located in Son Trach, Bo Trach district, Quang Binh province of Center Vietnam. Son Doon Cave is one of the largest natural cave ever found in the world. Who first discovered as a peasant named Ho Khanh. In 1991, he happened to shelter in this cave while looking deep into the forest.

This episode is also available as a blog post: 

https://railwaycafe.travel.blog/2021/07/02/the-worlds-largest-cave-in-the-world-son-doong-cave/