A 16th-century fountain marks the site of a lost medieval cemetery once filled with mass graves.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

Pitié-Salpêtrière was the dumping grounds for women who received the dreaded diagnosis of "hysterical."

In the best of all possible worlds, everyone will get a chance to see this statue in which Voltaire's heart is interred.

This former “ante-chamber to the guillotine” has been refurbished to illustrate the brutal history of French justice.

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

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

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

The celebrated eyesore created by starry-eyed sweethearts.

The pioneer of psychoanalysis spent the final year of his life here, still seeing patients on that famous couch.

This massive collection of British military artifacts includes the heartbreaking personal letters of the men in the trenches of WWI.

Scattered throughout London are ancient remnants of the city's former bounding wall.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

The curios of pharmacist and collector Henry Wellcome.

Originally built for London’s cab drivers, this bright green hut now serves anyone a hot drink or meal.

Hidden beneath the streets of London is a secret subway that only carried mail.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

A surreal statue honoring Prague's favorite literary son.

Increasingly decayed figures stand as a powerful reminder of the human costs of Czech Communism.

An eerie, existential museum dedicated to the author of "The Metamorphosis."

This automated sculpture of two men peeing will spell out text messages with their micturition.

A mocking tribute to the past and modern leadership of Prague.

A bust of Franz Kafka spins in pieces, reflecting the writer's inner torment.

Despite attempts by local police to discourage it, Beatles-inspired graffiti has been a means for artists to air grievances for decades.