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

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

The ruins of a Duke's bucolic dream, where camels once roamed alongside "Dutch" windmills and faux-Italian vineyards.

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.

The history of radiation is on safe display at the foot of a radiation science laboratory.

Down a cobblestone alleyway is a museum dedicated to Romanticism, with a secret garden.

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

This museum houses an imposing skeleton army comprised of creatures great and small.

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

Statue of death tucked in the University of Medicine courtyard.

Medieval museum built over Roman baths that features famous tapestries of a lady and a unicorn.

A museum on the history of Paris, including a set of Napoleon's toiletries, Proust's room, and relics of the Revolution.

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

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

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

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.

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

A surrealist timepiece by the artist of melting clocks.

A museum of magic with a Sadist past.

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

A mechanized clock where a man fights off a dragon, crab, and rooster.

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

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