From the deep ocean floor to vast underground caverns beneath our feet, these places challenge our understanding of the world.

Sơn Đoòng Cave is the world's largest cave in Vietnam, featuring a jungle, a river, and towering chambers that reach over 200 ...

The Hranicka Abyss is at least 1,325 feet deep, and likely goes down further. — -- A team of explorers believe they have discovered the deepest known underwater cavern the world in eastern Czech ...

Hells Canyon, the deepest river gorge in the United States, likely got rapidly carved 2.1 million years ago when a shifting landscape in Idaho caused a giant lake to start overflowing. That's ...

Discover the reasons behind the tragic fate of an explorer in the world’s deepest cave. Major Bay Area sideshow crackdown: 22 cars seized, felony arrests made in sweep ...