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

The tragedy of the Japanese internment camps is remembered here by a stark "Soul Consoling Tower."

Ruins and statues dot the landscape of this tiny island rich with royal history.

This whimsical castle of grottoes was the labor of love of a French postman, and one of the greatest achievements of outsider architecture.

This mountaintop beacon is only lit three times a year but shines like some kind of all-seeing eye.

Looking like nothing more than a cartoon deserted island, this tiny sandbar is home only to a single umbrella.

This strange geological landscape erupts with sudden bursts of water.

This former Welsh metal factory is now a lovely abandoned relic but was once one of the industry's world leaders.

The maritime museum that boasts the largest nautical library in the western hemisphere.

An elaborate Mayan city shrouded in alien conspiracy revealed the tomb of Pacal the Great.

A museum collection honoring the long history of the FDNY is held in a disused Manhattan fire house.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

Down a cobblestone alleyway is a museum dedicated to Romanticism, with a secret garden.

Once America's longest-manned military fort, now an abandoned hulk.

Holding multiple historical boats and an entire 19th century village, this New England attraction is the largest maritime museum in the world.

Artifacts of whaling, with both its perils and adventure, are housed in this museum in a former candle factory.

This Italian-style temple replica has been threatening to fall off the Irish coast for hundreds of years.

This pebble beach is so beautiful that taking its rocks is against the law.

A curious whirlpool formation supposedly capable of entangling or engulfing branches, tree trunks, or whole rafts full of hapless tourists.

The ruins of an ancient Mayan city, beautifully preserved and only accessible by boat.

Yale University's home for rare works, including the mysterious Voynich Manuscript.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

A once grand hotel is being retaken by the wilderness it once capitalized on.

This replica Viking village was created for a film that was never shot and is now open to visitors.