The ruins of the "20-year town" lay out among the mountains of Alberta.

Hidden beneath the streets of London is a secret subway that only carried mail.

Ruins of the elaborate house where the enigmatic costume designer threw glamorous parties for New York's theatrical elite.

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

America's first public mental health facility.

A tourist attraction founded around a slumping cabin.

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

Not even a series of devastating fires could keep this odd castle in upstate New York from bouncing back.

Ruined castle with subterranean vaulted Goblin Ha' or "Goblin Hall."

A remarkably intact castle that once was the largest in Ireland.

Once the gateway to the utopian dream-village of a Civil War embalmer.

Visitors dip into a variety of pools of what was once ice.

Nightmarish example of the unintended consequences of weapons testing.

Quirky castle designed by the American actor best known for portraying Sherlock Holmes on stage.

A beautifully eclectic mix of architectural styles.

Ancient rock-hewn town that witnessed key events of Georgian history.

The home of one of America's most wealthy industrialists is now a historic site that remembers a more decadent time in the country's history.

This fantastical icy castle is built anew every winter.

Mysterious Spanish catacombs of unknown origins.

Created hundreds of years ago, the magical follies and landscapes at this park were almost lost to time before being restored.

A turn-of-the-century architectural marvel built on healing mineral springs and salt licks.

A fairy tale castle in modern Rome.

Cursed swimming pool left abandoned is now a favorite of filmmakers and ghost hunters.

Florida castle built with aluminum printing plates.