Though these human-made islands were constructed as an escape for the wealthy, they rarely see many visitors.

This precariously perched fortress was once ruled by a crow-worshipping baron.

Legends of treasure and spirits flow from this this fairy tale-like oasis.

An engineering error ensured this cavernous 350-foot-long subterranean thoroughfare was never used as intended.

If you’ve ever seen a picture of Machu Picchu, then you’ve seen a picture of Huayna Picchu—you just didn’t realize it.

This odd Chilean waterfall-cano hotel must be entered via a rope bridge.

This Japanese-inspired labyrinth of hot springs is hidden in a Chilean forest.

Modern Japanese museum is buried by snow annually.

The vast chamber inside this abandoned cooling tower looks like something out of a sci-fi dystopia.

Museum of science fiction, utopias, and extraordinary journeys of the mind.

A 300-yard long natural tunnel runs through a ridge deep in the Appalachian Mountains.

A 14th century bridge built as a fortress, where the devil lurks on one of its towers.

A breathtaking bridge that crosses a vast gorge over a river's torrents, and has a tale of a devil architect attached.

Along the Rhine, about a mile from the historic Munster, learn the heartrending story of two lovers torn asunder, cast into unknown layers of time and space.

This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.

Once described as the "Eagle's Nest," this ruined ancient city rests on a remote mountaintop.

An abandoned saucer-shaped monument in the Bulgarian mountains.

Peek through a transparent pyramid and drink in the mountain made of books.

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

This floating garden in the sky is straight out of a fairy tale, but the real thing is nothing short of magical.

Huge stone depressions which may have acted as an Incan agricultural experiment.

The world's largest natural arch was forgotten for over 50 years after its discovery.

Five mile wide circular ring of rock in the Russian Far East is a curious geological oddity.

A remote forest of stone pillars along the Lena river.