A crumbling hospital from the 1850s on Roosevelt Island.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

Not-so-fearsome tiny trolls live under this wooden train trestle in Portland.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

Stripes of human ashes cover a back lawn in the most sought-after burial grounds in Paris.

Collection of antique taxidermy and natural specimens, near one of Paris's oldest flea markets.

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

This Paris art space celebrates the creativity and ingenuity that springs from abject poverty, especially in Africa.

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

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

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

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

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

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

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.

A majestic lion statue guards this Parisian botanical garden, and feeds on an unsettling item.

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.

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

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

The very center of Paris is surrounded by a bevy of strange good luck rituals.

A horde of stray cats rule in this secluded Parisian cemetery under a bridge.

The oldest stone house in Paris was built by its most famous alchemist.

Abandoned railway line circling the city of Paris.