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

The oceanic dumping ground where spaceships go to die.

These tombs were built into the side of a mountain so that ancient angels could reach the dead.

The world's largest man-made underground caverns offer unparalleled underwater wonders.

Largest collection of mounted dinosaur specimens in the world.

Japan's corrupt-mental-institution themed restaurant offers diners a chance to eat inside of filthy cells.

Each year these high desert hills are absolutely covered with poppy flowers in a surreal show of nature.

Historical Japanese-Dutch relations are honored with haunted rides and flower fields in this replica town.

Erotic art covers the walls of the largest ancient pleasure palace.

Beasts and branches swirl in sandstone carvings, interrupted by one strange creature.

This series of Armenian caves held the oldest brain, shoe, and winery in the world.

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

A subterranean Holocaust refuge within one of the world's longest cave systems.

The world's largest statue of Mao Zedong looks out over the city where he discovered Communism.

Tucked behind the Institute of Neurological Science down a decrepit street resides the largest display of human brains in Latin America.

A bloody history is captured in this former prison turned museum.

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

Gladiators battle and chariots race daily in the ruins of a once-great Roman city.

Natural sonic phenomenon comes with a grisly legend of murder and blood.

A rocky Irish outcropping with a history of wealth, conflict, and ruin.

A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

This natural spring not only claims to heal the wounded but it has also been willed to God.

A preserved dragon's rib that remembers the legend of the founding of the city of Atessa.

Twelve natural mummies are displayed in the crypt of this former monastery school.