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

Fantastic stories on a miniature railroad.

A small but immensely extravagant palace built by the "Night King."

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

The fairy tale castle of the "fairy-tale king."

Enter the Forest of the Elves.

Abandoned city hidden from the world by tropical forest and isolation on the coast of Kenya.

An alchemist's "magic door" stands in the middle of a Roman park.

A whimsical antique shop with a strong air of mystery, filled with items from ages, and what feels like worlds, past.

Below a historic English market town lies a secret underground city complete with kitchens, laundries, storerooms, and an underground lake.

The largest of London's subterranean rivers and once a mad, bad center of London life.

A still functioning vaudeville carousel that has operated for over a century boasts a colorful menagerie and past.

This "floating railway" is one of the world's oldest monorail systems.

Eclectic collection of dark and macabre antiques.

Seattle's own bad art museum located inside Cafe Racer.

An often-shuddersome journey into a low-tech, robotic themepark.

A house filled to the brim with oddities and curiosities.

"I did this all while you were watching TV."

A Circus legend leaves an unexpected endowment.

A large circus museum with summer performances.

Hundreds of hidden passageways weave through the old quarters of Lyon.

Holy Grotto of Montserrat Monastery holds one of Europe's mysterious black Madonnas.

The "Mystery and Company of Merchant Adventurers" is an Elizabethan-era hangout in Moscow.

A well-preserved network of cavernous tunnels have spent silent centuries removing Toronto's waste.