Stalactites and stalagmites in a beautifully lit cave.

A gargantuan crystal kingdom.

Bermuda triangle lighthouse, site of mysterious disappearances, left to crumble into the Atlantic.

A cave network located at the southernmost tip of mainland Greece was once believed to be an entrance to Hades.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

Huge concrete structures designed as an early warning system for Britain to detect enemy aircraft.

Natural time capsule containing an alien ecosystem.

Remember that scene in the Matrix, when Neo is in the big white room with all the weapons flying by? Well, this is what it would look like if he had wanted trees instead of guns.

A Hawaiian stairway to heaven—that you can't climb.

A tunnel dug through the side of a mountain by hand provides convenient yet death-defying access to a small village in China.

A natural arch offers panoramic views of Yangshuo's karst hills.

Snow-capped peaks, colorful waterfalls and stunning vistas on the edge of the Himalayas.

The world's highest and most dangerous infinity pool lies at the precipice of Victoria Falls.

A total of 999 stairs lead visitors through a massive hole in a mountain known as the Gateway to Heaven.

Not one, not two, but three natural bridges remain in this captivating spot post-sinkhole.

For those with no fear of heights: a skywalk 4,700 feet up on a Chinese mountain.

The ancient settlement attracts tourists from all over looking to learn about the Chinese vision of the afterlife.