A spectacular cave and a beguiling lake.

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

A perfectly circular lake is formed by the crater of an ancient underwater volcano.

A small Portuguese cottage formed between boulders in the countryside.

A unique seaside cave where Aleister Crowley faked his own death.

This small chapel is built of human bones and decorated with a golden skeleton.

A 16th century chapel decorated with bones, skulls, and entire bodies hanging from the wall.

A stately palace has been converted into the world's largest cannabis museum.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

Local lore says the devil built this beautiful medieval bridge to help a fleeing bandit.

Houses are tucked between, on, and underneath giant boulders.

This futuristic observatory at the top of the Pyrénées offers unrivaled views.

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

This century-old ruined temple was reborn as "The Church of Skate."

One of the largest ossuaries in Spain is packed from floor to ceiling with bones.

This awesome Spanish castle is so fantastical it was actually used on Game of Thrones.

The hermits of Karoulia protect their asocial lifestyles by living on the vertical face of a treacherous precipice.

This taxidermilogical collection was assembled by a peltmonger turned animal activist.

Artworks by loners, prisoners and the criminally insane.

Over 3km of caverns and caves at the Switzerland-France border contain the largest underground river in Central Europe.

Museum of science fiction, utopias, and extraordinary journeys of the mind.

One hundred years ago this small house in downtown Zürich became the birthplace of the Dada movement.

Traversing steep Alpine slopes, this engineering marvel is one of the longest and highest funiculars in the world.

A historic observatory precariously perched at the "Top of Europe."