Sweetwater, Tenn.? When a 13-year-old boy discovered what is now the world’s second-largest underground lake, he had to crawl through a muddy hole deep inside a cave and throw balls of dirt into ...

Traverse 330 steps on the way to such distinctive chambers as the “Devil’s Kitchen” and the “Crystal Vault.” Wild caving ...

With its breathtaking scenery and sense of adventure, Cave of the Winds is a must-visit for anyone seeking to explore the ...

Most people think of visiting big cities, national parks, and beaches when they plan a U.S. trip. There’s hardly anyone who’s ...

Sistema Sac Actun (Mexico) – Located in the Yucatán Peninsula, it's one of the world’s longest underground rivers, connected to ancient Mayan cenotes. Lost River (USA – Indiana) – This river vanishes ...