Venture into the hideout of one of Hong Kong's legendary pirates.

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

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

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

England's most notorious suicide spot.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

Roman ruins top white travertine terraces formed by ancient hot springs.

Tubing through a cave lit with glowworms is a magical underground experience.

These fantastically named natural pools look like something out of a Scottish myth.

A complex of six forts embedded in the Rajasthan hills.

Unique geological formations in China, featuring some suggestive shapes.

This "floating island" plateau sits 7,671 feet above the forest floor.

A gargantuan crystal kingdom.

Most-visited and most-photographed slot canyon in the American Southwest.

A seemingly endless landscape of pure salt stretches far across Bolivia.

Breathtakingly blue walls shimmer inside the "Glacier Behind the Town."