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.
Cave of Swallows (Mexico)
Located in the state of San Luis Potosí, Mexico, this pit cave is popular with ornithologists and adrenaline junkies. The former come to marvel at the clouds of birds – swifts to be exact – clinging to the cave walls, which also serve as breeding ground for parrots and parakeets. The latter base jump 330 meters down the perfectly vertical chamber to the guano-caked ground below. The view from the bottom is as daunting as it is feathered.
Credit: Onixmtz / Wikipedia