This Parisian gem is one of the most incredible ethnographic museums in the world.

A modern-day Lascaux cave underneath Paris.

The ruins of a Duke's bucolic dream, where camels once roamed alongside "Dutch" windmills and faux-Italian vineyards.

A museum on the history of Paris, including a set of Napoleon's toiletries, Proust's room, and relics of the Revolution.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

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

Egyptian Revival movie palace abandoned for decades and restored in 2013.

Behind the pink curtain, Au Bonheur du Jour, an art gallery of erotic archives.

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

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

A haunting collection of the vanished and disappearing natural world.

One of the oldest medical collections in Europe focusing on rare surgical instruments.

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

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

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

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

Notorious artist squat renovated into legal studios.

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

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

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

The history and future of cannabis.

Have fun at the world's first Buddhist waterslide park.

A 98-room castle in the middle of Toronto that bankrupted a 19th century electricity multimillionaire.

An annual extravaganza of Broadway theater memorabilia.