Inside a former cabaret, seven floors of erotic art.

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

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

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

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

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

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

The celebrated eyesore created by starry-eyed sweethearts.

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

Gargantuan home of Russian science.

Dozens of padlock-trees along the Moscow River.

Thirteen sculptures in central Moscow graphically depicting vices of the modern world.

World's largest bell sits on the grounds of the Kremlin in Moscow.

Stalinist skyscraper built with help of cryotechnology.

Stalin's march toward a more modern USSR flooded a monastery, leaving a unique and extravagant nautical marker, "The Flooded Belfry."

Stunning examples of Russia's 18th-century wooden architecture.

Hear the quietest sound from across the dome.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

An 18th century wonder of the world, lost in WWII, re-created at the Catherine Palace.

A 250-year-old timepiece-automaton adorned with golden mechanical birds, which still sing to this day.