Incredible labyrinth of man made caves.

This collection of solar timekeepers includes the world's first digital sundial.

What was once a bustling mining installation is now a bustling hub of contemporary art.

This banal Parisian entranceway is not what it seems.

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

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

Despite being considered a thoroughly American sport, basketball's oldest surviving playing field is found in the basement of a Paris YMCA.

The floorboard scrawling of a tragic madman is on public display outside a Paris hospital, much to the dismay of its opponents.

Museum on French naval history, with magnificent figureheads, a historic diving suit, and a boat used by Napoleon.

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

This life-size replica of the Statue of Liberty's flame is also a tribute to Princess Diana by default.

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

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

Where the high court feasted, frolicked, and high courtesans put their royal lovers' diamonds to the test.

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

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

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

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

The first green space constructed on an elevated viaduct.

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

This Parisian café sticks almost exclusively to an ethos of reuse.

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

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

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