A museum dedicated to linguistics, from how babies learn to talk to endangered and extinct languages.

A simple plaque on the facade is the only reminder that the treaty ending the American Revolution was signed inside.

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

In this Parisian garden's grotesque former life as a zoo it fed exotic animals to the bourgeois and put humans on exhibit.

A lone cannonball remains lodged in the walls of the Hotel de Sens as a sober reminder of a revolution.

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

Walk through spectacular aisles of hanging meat and wagon wheel–sized cheese at the world's largest wholesale food market.

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

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

This statue was given to France by the United States to commemorate the centennial of the French Revolution.

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

A haunting collection of the vanished and disappearing natural world.

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

Abandoned railway line circling the city of Paris.

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

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

The attic of a four-century-old canal house hides a clandestine church.

This subterranean studio is filled with fascinating kinetic art.

This bird-loving brewery is situated in an old municipal bathhouse, nestled beside a 300-year-old windmill.

Famed for its pie, this eatery has a hidden tunnel that allowed Catholics to secretly walk to church during the Reformation.

A curious collection dedicated to human and animal anatomy and pathology.

This museum inside Amsterdam's largest cemetery explores how people deal with death.

The first museum in the world devoted to sexual gadgetry.

Berlin's old airport.