The world's oldest bookshop still in operation.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

An immersive projection art installation uses sound, scale, and light to take visitors inside classic works of art.

The personal library of the founder of modern neurology is open to visitors.

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.

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 subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

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

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

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

"In the Dark" Restaurant in Paris offers dinner in complete darkness.

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

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.

A haunting collection of the vanished and disappearing natural world.

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

Paris' linguistic guide to the international language of, yes, love.

A museum of carnival attractions where you are invited to ride the rides.

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

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

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

This eatery re-creates dishes from the Ottoman Empire so you can dine like a sultan.

The legendary luxury train passage is commemorated with a charming museum inside its former eastern terminus.

No one is sure if the world's fourth-largest diamond had been found in a rubbish heap or was pawned by Napoleon's mom.