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

Breathtakingly blue walls shimmer inside the "Glacier Behind the Town."

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

Hideout of thieves, monks, and goat-footed gods.

The hallucinogenic center of the ancient world.

Swarms of dainty flying insects swarm into the Petaloudes Valley to get busy.

A minotaur, a labyrinth, and a dubious restoration pull in visitors from around the world.

A curious cave church carved into the face of a cliff.

A sprawling nature preserve harbors the world's only living dragons.

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

Sealing couples' love since just after World War I.

Monasteries on rock pillars, once accessible only by frayed ropes.

The small cliffside monastery known as the Tiger's Nest is said to be the meditation site of an 8th-century Buddhist master.

A dismembered holy head stares out from her beautiful reliquary at the St. Dominic Basilica.

Geothermal waterfalls in Tuscany.

This giant boulder is pinched over a 1000-meter abyss by two mountains.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

A seemingly endless landscape of pure salt stretches far across Bolivia.

An underground city of salt.

Real bones which are said to have belonged to a Polish dragon.

Roman ruins top white travertine terraces formed by ancient hot springs.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

The largest stone moai on Rapa Nui.

An ancient capital city that dates back 3,000 years old and harbors many surprises.