The celebrated eyesore created by starry-eyed sweethearts.

A 16th-century fountain marks the site of a lost medieval cemetery once filled with mass graves.

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

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

A curious collection of locks and keys.

The remaining relics of the patroness of Paris lie in a chapel under a striking double spiral staircase.

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

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

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

This little-known relic crypt holds stolen parts of a Roman Empress.

A popular shrine where the Blessed Virgin allegedly appeared in 1830, displaying a holy armchair and two incorruptible remains of Lady Saints.

Two awe-inspiring globes from the reign of the Sun King hang from the ceiling of France's national library.

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

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

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

The largest medical and anatomical collection in France lies hidden from the public.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

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.

Indents in the pavement are all that remain from a grisly death machine in Paris.

Known as the "Dodo Manège," this carousel features a herd of animals that have disappeared—or may be gone soon.

France's national museum of scientific and industrial instruments.

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

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

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