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

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

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

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

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

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

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.

France's most famous cemetery, with some of its most curious tombs.

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

The recovered bones of martyrs slaughtered during The Terror are on display in this church crypt.

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

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

Pitié-Salpêtrière was the dumping grounds for women who received the dreaded diagnosis of "hysterical."

A modern-day Lascaux cave underneath 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 subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

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

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

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

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

A surrealist timepiece by the artist of melting clocks.

A museum of magic with a Sadist past.

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

A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.