An elegant chandelier hangs over this ancient sewer chamber, now open for concerts and public tours.

A church filled with the bones of hundreds of virgins martyrs—or so they say.

BDSM, 1930s Style.

Got apples?

A modern-day Lascaux cave underneath Paris.

Hidden away in a modern library are the remains of one of the 18th century's most celebrated wunderkammers.

This Parisian café sticks almost exclusively to an ethos of reuse.

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

The very center of Paris is surrounded by a bevy of strange good luck rituals.

Paris' linguistic guide to the international language of, yes, love.

Notorious artist squat renovated into legal studios.

The macabre collection of Jacques Sirgent, an expert scholar on the undead and all of their trappings.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

Abandoned railway line circling the city of Paris.

A brush maker used his factory to protect blind Jews from the Gestapo.

What started as a tongue-in-cheek shrine is now a full-blown museum celebrating "The Hoff" and his longtime love affair with Berlin.

A 12th-century fortress containing some of Berlin's oldest buildings.

A narrow passage next to a cafe leads to a courtyard exploding with murals, tags, and paste-ups.

Floating swimming pool within a moored vessel.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

This Berlin island is home to a flock of free-roaming peacocks, as well as a historic ivory folly.

This classic restaurant features a gorgeous mirror-clad room.

A slice of central Asia in the middle of Berlin.