This natural French spring has been turned into a magical grotto by Roman and medieval constructions.

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

An off-the-beaten-path boutique stuffed with an eclectic collection of upcycled goods.

A modern-day Lascaux cave underneath Paris.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

Notorious artist squat renovated into legal studios.

A subterranean display of public art and architecture.

This unique exhibit "Dialogue in the Dark" reverses roles as the visionless become guides and the sighted become ‘blind.’

Crop circles inspired this whimsical garden in Germany.

An ornate century-old elevator still connects the two halves of Bad Schandau.

The world's tallest church tower reveals a spectacular view to anyone up to the task of climbing the daunting staircase.

The architect of this fanciful complex called it an "oasis for humanity and nature in a sea of rational houses."

Bursting forth from a historic German neighborhood, these day-glo palaces are now a bright fixture in the town.

You haven’t properly toured a winery until you’ve slept in an actual wine barrel.

An industrial relic is now one of Europe's most staggering art spaces.

Dress up like a miner and take a slide into the disco-lit depths of this once foundational salt mine.

This former steel and coal plant is now a neon-lit industrial fantasia.

It's always summer at the beach inside this former airship hangar.

A German apartment building hosting as many trees as human occupants.

What was once thought to be a wellspring of unicorn bones is actually just a prehistoric burial site.

These 18th century gardens tell a rocky story of the son of Odysseus.

No need to strap in for a "ride" on this walkable roller coaster.

This little museum is making sure that the art and history of the graffiti sticker is not scraped from history.