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

A slice of central Asia in the middle of Berlin.

An enormous concrete structure built over a nuclear crater.

This natural French spring has been turned into a magical grotto by Roman and medieval constructions.

Come stay at a live-in art installation.

Fall down the rabbit hole into a surreal journey of human consciousness "from ass to soul."

This little museum is making sure that the art and history of the graffiti sticker is not scraped from history.

Berlin's oldest surviving academic architecture hosted decades of animal dissections.

Architect Le Corbusier built his friend a cubist house to match his impressive collection of cubist art.

This exemplar of modernist architecture is meant to captivate and inspire students of the Cooper Union.

This little museum is built on a theater that was once a wildly elaborate speakeasy.

Salute the leader of the proletariat.

Hear the quietest sound from across the dome.

Giant, friendly pelicans in Central London, the most unlikely of places.

A mysterious artist-run cabinet of curiosities and library.

Dictionary Johnson’s favorite feline.

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

On the top floor of an upscale department store stands a lavish restaurant housed in a replica of a luxury French dining car.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

A Gothic cathedral created from volcanic rocks.

A museum dedicated to exhibiting remarkable outsider art.

The site of the famous Nazi book burning campaign of 1933 remembers its "Night of Shame".

Open-air museum with an elaborate sculpture garden, stretching for over 70,000 square-meters.

Even France's favorite aquatic son Jacques Cousteau, couldn't get to the bottom of it.