This innocuous-seeming building is actually the remnant of a major wartime brothel.

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

The headless bodies of more than 1,300 guillotined victims of the Reign of Terror are buried here in mass graves.

Where the high court feasted, frolicked, and high courtesans put their royal lovers' diamonds to the test.

This structure atop a craggy cliff in one of the most beautiful parks in Paris boasts an unbeatable view.

This banal Parisian entranceway is not what it seems.

An off-the-beaten-path boutique stuffed with an eclectic collection of upcycled goods.

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

Indents in the pavement are all that remain from a grisly death machine in Paris.

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

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

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

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.

On the eve of a condemned prisoner's death, this bell rang 12 times outside their cell.

The storied English village that pretended to be insane inspired NYC's nickname and the fictional namesake in the DC Comics universe.

A collection of machines designed to break things for science.

A hundred copies of Antony Gormley's naked body stare out across the water.

The majority of the museum's large collection is held in a storage space open to the public a few times a year.

Grab a cuppa at England's first and only domestic tea plantation.

This landmark church concealed a crypt packed with bones that was discovered thanks to the London Blitz.

A collection of full-size movie monsters opened to the public.

The only surviving sidewalk clock in Brooklyn.

The oldest living organism in New York City. Maybe.