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

Once a 19th-century brasserie, this McDonald's exterior celebrates Alsatian design and the "King of Beer."

A lone cannonball remains lodged in the walls of the Hotel de Sens as a sober reminder of a revolution.

A series of abstract, silly sculptures represent the works of a great modern classical composer.

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

This frog-themed restaurant was frequented by Picasso, Saint-Exupéry, and more.

This former “ante-chamber to the guillotine” has been refurbished to illustrate the brutal history of French justice.

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

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

In the best of all possible worlds, everyone will get a chance to see this statue in which Voltaire's heart is interred.

An overlooked marble is the only surviving in-place 18th century example of the measurement that changed how we define distance.

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

Behind the pink curtain, Au Bonheur du Jour, an art gallery of erotic archives.

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

Walk upon the mementos of the dead in this Parisian courtyard paved with medieval tombstones.

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

A counter-culture bookstore like no other hides in plain sight in the streets of Paris.

This massive library holds what was once the largest book collection in the world.

Notorious artist squat renovated into legal studios.

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

Climb inside an iron crystal magnified 165 billion times its normal size.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

This noble mash-up in eastern Luxembourg is part Medieval, part Renaissance, all castle.

This tri-part waterfall is a little bit of fairytale beauty in the heart of Luxembourg's Little Switzerland.