The ruins of an ancient mansion sits in front of and underneath a contemporary art gallery.

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

This recessed garden protects thousands of mountain plants by creating its own microclimates.

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

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

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

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

Remains of Roman amphitheater hidden in a sleepy quarter of Paris.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

The first green space constructed on an elevated viaduct.

How did a French journalist’s grave become the sexiest statue in the cemetery?

A grotto-like lodge decorated with gilded mosaics, rocks and a noisy waterfall was the setting for the most sumptuous pleasure house of 1900s Europe.

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

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

The ruins of a Duke's bucolic dream, where camels once roamed alongside "Dutch" windmills and faux-Italian vineyards.

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

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

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

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

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

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