The only residents of this abandoned housing development full of identical castles are stray cats and dogs.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

This rusting remnant of the local herring industry is being given a second life.

This natural Icelandic fissure allows divers to swim right between two volatile tectonic plates.

Personal garden filled with mosaics made of recycled garbage.

An art world insider finds himself battling for his artistic home.

An enchanting work of outsider art, full of whimsical sculptures and carvings.

The deserted pirate-themed restaurant still entices explorers.

A self-built mosaic house and sculpture park.

Ghosts of France's colonial past.

A mosaic-tiled house built by graveyard sweeper Raymond Isidore.

The fantastic architectural models of a French traveler.

This professional clown's home is an outsider art wonderland.

A well-preserved medieval village nested on a rocky outcrop and surrounded by a network of cliffs, natural bridges and canyons.

The largest underground church in Europe.

A cave dwelling that was started by the Celts, expanded by monks, and finished by knights.

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

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

The ruins of a medieval castle linked to the murderous French lord that inspired the famous legend of Bluebeard.

A tiny, remote island packed with wonders both natural and geeky.