The design of this beautifully crafted building was inspired by Norwegian glaciers.

Former hunting lodge of a duke who was an avid collector of impressionist works.

The Argonaute submarine was the French navy's pride and joy in the 1950's.

A museum which takes visitors to the côté obscure of Paris.

BDSM, 1930s Style.

This banal Parisian entranceway is not what it seems.

Noirish green neon marks the location of one of the oldest private detective agencies in France.

A modern-day Lascaux cave underneath Paris.

A font of vintage porn on the silver screen.

The curious underground history of keeping Paris clean.

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

Down a cobblestone alleyway is a museum dedicated to Romanticism, with a secret garden.

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

Stroll through retro Paris while shopping for old postcards and discarded doll heads.

A mechanized clock where a man fights off a dragon, crab, and rooster.

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

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

Abandoned railway line circling the city of Paris.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

Annual technopop celebration of peace and love.

Apartment complexes built into huge repurposed natural gas tanks.

Vienna's underworld of tunnels and subterranean rivers made an iconic appearance in a 1949 Orson Welles film.

Legends surround an ancient tree trunk riddled with nails for good luck.

Located right outside of Vienna, visitors can take in expansive views of an ethereal forest.