Miles of man-made caves and tunnels are currently used for cultivating mushrooms.

This emotive sculpture was originally created for the 1878 World's Fair.

An Orthodox church built by the Royal Family for the Russian community exiled to the French Riviera.

A French library that makes sure its love of books is writ large... giant in fact.

A beautiful Victorian statue shows France's enduring love of the rhinoceros.

This mural painted by Keith Haring was done without payment as a gift to entertain the children at the Hôpital Necker.

Claude Monet was baptized in this lavishly ornate Paris church.

Hundreds of secret cabinets built into the walls of legendary poisoner's private work room.

The video game-themed street art first popped up in the French city.

A 400-year-old church covered floor to ceiling in ex-voto offerings from the faithful.

An unusual number plate signifies the building's saucy past.

One of Jeff Koons’s largest sculptures and his first commemorative work.

This lesser-known Frank Gehry building houses a treasure trove of cinema history.

A French artist's vague warning hangs over Belleville.

This stunning French estate was so lavish that it landed its original owner in jail for the rest of his life.

Ordinary art transforms to extraordinary thanks to locals' quirky sense of humor.

The world's largest reflecting pool is just two centimeters deep.

A beautiful and classically designed villa, with an hourly infestation of monsters.

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

This ancient Roman bridge and aqueduct still stands as a wonder of classical construction.

Former hunting lodge of a duke who was an avid collector of impressionist works.

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

This bridge was constructed from the rubble of the infamous Bastille.

A museum dedicated to one of Paris’s most famous residents, tucked into a corner of one of the city’s most famous squares.