For tens of thousands of years, caves have captured and fostered the human imagination. They're the closest thing to an alien world most of us will ever experience, and much like the bottom of the ocean, they continue to demonstrate how little we know about our own planet. Here's a look at some of the world's most stunning, inspiring, and spectacular caves.
Ellison's Cave (Georgia, USA)
Caves are often measured by the structures they could hypothetically contain. Fantastic Pit in Ellison's Cave, the deepest in the U.S., could engulf the Washington Monument. Plunging 586 feet beneath the surface of Pigeon Mountain in Georgia, the pit is open year-round, but should only be entered by experienced climbers. At least three people have died of hypothermia after being trapped in the pit and another fractured his skull and femur after plummeting 30 feet in 2013.
Credit: Stephen Alvarez / National Geographic