By Marie-Lan Nguyen

These sinkholes in Mexico were formed during the ice age and were held sacred by the Mayans.

To Sua is a giant hole in Lotofaga that was converted into a swimming pool with water flowing through a lava-tube tunnel.

This railway engulfed in a tunnel of leaves is a Pinterest favorite and a Ukrainian hot spot for lovers. Although it’s undoubtedly romantic, there is an active train that travels through the tunnel three times a day to deliver wood to a factory. Just...

This 355-foot waterfall lies at the border of Zambia and Zimbabwe and it is the widest waterfall in Africa. There’s also a famous feature on the Zambian side called the Devil’s Pool, which allows adventurous tourists to hang out at the edge of the fa...

Son Doong is the world’s largest cave, created 2–5 million years ago. A half-mile block of 40-story buildings could fit inside it!

By F Mira