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.
Lechuguilla Cave (New Mexico, USA)
What sets Lechugailla Cave apart from others isn't size but its diverse and pristine formations: shelfstones, calcite columns, cave pearls, soda straws, gypsum-frosted stalactites, and enough stalagmites to make the most jaded geologist swoon. Despite being known for years, Lechuguilla was largely ignored until cavers uncovered extensive passages in 1986. More than 136 miles of underground passages have been discovered since then, but only teams conducting scientific research and exploration are allowed to enter.
Credit: Dave Bunnell / Wikipedia