One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

This house's itty bitty size means no humans allowed.

The world's oldest bookshop still in operation.

Puppet theater and museum holding a collection of more than 300.

From toys to kettles to scientific instruments, this German museum celebrates the beauty of 20th century design.

The music is over at the Ballhaus Riviera Ballroom, but the ballroom remains in haunting disrepair.

A state-of-the-art medical facility from the Imperial era is now a derelict ruin.

A surreal museum of extraordinary industrial objects.

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

This classic restaurant features a gorgeous mirror-clad room.

Dedicated to the art of hunting, with juxtapositions of contemporary art.

This museum houses an imposing skeleton army comprised of creatures great and small.

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

A favorite Paris bar for U.S. expats, including Gershwin, Hemingway, and James Bond.

"In the Dark" Restaurant in Paris offers dinner in complete darkness.

A haunting collection of the vanished and disappearing natural world.

A counter-culture bookstore like no other hides in plain sight in the streets of Paris.

A museum of carnival attractions where you are invited to ride the rides.

This massive library holds what was once the largest book collection in the world.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

Abandoned railway line circling the city of Paris.

France's most famous cemetery, with some of its most curious tombs.

Notorious artist squat renovated into legal studios.

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