Explore the ancient caves of Hang Son Doong, Vietnam. Hang Son Doong is one of the largest caves in the world and features a fast-flowing underground river. For spelunkers, exploring Hang Son Doong is the equivalent of scaling Mount Everest.
Rocamadour, France is built on a rock in the middle of the Causse de Gramat. This is a vast slate plateau and part of the Causse du Quercy. The city is the most visited pilgrimage site after Lourdes in France.