A medieval church with largest and oldest collection of Renaissance frescoes in France.

A French valley with forests so lush it was nicknamed "the Small Amazonia of the Pyrenees."

Beneath the city of Lourdes, France is a massive, concrete church.

A landscape decorated with enormous skull sculptures.

This huge abandoned fortress hidden inside a mountain holds a world of subterranean secrets.

A Franco-era dam flooded (almost) everyone out of this centuries-old Aragonese town.

Sanctuary on a ridge near an ancient shrine to a "Black Madonna" built by the founder of Opus Dei.

An arresting arch punched straight through a mountain provides one of the most scenic spots, and challenging climbs, on the planet.

Abandoned Nazi train station turned underground astroparticle laboratory.

Abandoned 18th century weapons factory in the Aezkoa Valley.

This Navarrese cave's history of witchcraft and pagan ritual is not just embraced, but recreated each year.

A museum dedicated to the Spanish occult in a town that was terrorized by the Inquisition.

An eerie, derelict amusement park in Berlin.

Vietnam's feral abandoned water park offers access to a post-apocalyptic funscape, now with fewer crocodiles.

Hang out with thousands of butterflies in one of the world's largest such enclosures.

Kuala Lumpur’s historic single-screen cinema, transformed into a labyrinthine bookstore.

Come for the chanting, stay for the monastical vegan buffet.

This former factory turned private museum contains surreal and creepy artwork created by Robert Y.

A secret passageway from World War II is now a quirky pedestrian shortcut.

One man's hand-sculpted collection of colorful masks representing a host of gruesome spirits.

This Taiwanese promontory is covered in otherworldly hoodoo formations.

A rare pod of derelict midcentury Futuro and Venturo houses lines a semi-abandoned beachfront resort outside Taipei.

A Buddhist temple covered in intricate designs and carvings made out of seashells and pieces of coral.

These charming mailboxes became social media stars after a typhoon failed to topple them.