Neversink Pit- can't believe I'd never heard of this place until today! "Neversink pit is a limestone sinkhole in North Alabama. It’s one of the most-photographed sinkholes in the world because of its beautiful fern-covered ledges and waterfalls.
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.