The former home of France's controversial pop maestro is almost completely covered in ever-changing tributes and graffiti.

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

This off-limits room in the National Library of France is home to a system of pneumatic tubes, once used to bring books to readers.

A Parisian exterminator's shop whose storefront displays stuffed rats hanging from traps.

France's national museum of scientific and industrial instruments.

The history of radiation is on safe display at the foot of a radiation science laboratory.

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

An all-American grocery store in Paris sells U.S. "cuisine" like Pop-Tarts and Heinz ketchup to homesick ex-pats.

A majestic lion statue guards this Parisian botanical garden, and feeds on an unsettling item.

Known as the "Dodo Manège," this carousel features a herd of animals that have disappeared—or may be gone soon.

This Parisian fountain is a little bit fantasy and a little bit nightclub.

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

Egyptian Revival movie palace abandoned for decades and restored in 2013.

What looks like a normal building is really a hollow facade hiding a subway vent.

A subterranean shelter remains intact under a busy Paris railway station.

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

This hidden workshop is filled with molds of France's most iconic sculptures.

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

1920's reinforced concrete church by architect Auguste Perret changes the face of modern design.

A hidden church in a hidden courtyard tells the story of the Miracle of Amsterdam.

One of Amsterdam's narrowest houses is located right across the canal from its widest.

This large copper bolt represents the benchmark for measuring sea levels in most of Europe.

Three connected pink triangles memorialize persecuted gays and lesbians throughout history.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.