A haunting collection of the vanished and disappearing natural world.

This modest marker near Notre Dame identifies the very center of Paris.

One of the oldest medical collections in Europe focusing on rare surgical instruments.

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

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

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.

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

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

Notorious artist squat renovated into legal studios.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

Abandoned railway line circling the city of Paris.

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

On a wall in linear London, a plaque hangs at the high water mark of one of the worst floods in fictional Kcymaerxthaereal times.

Three small rooms at the back of the “official” church of London's clowns.

An abandoned tank sits in an empty London lot as a symbolic middle finger to local city planners.

This hidden rooftop garden in downtown London offers a quiet respite from a bustling city.

This small museum in a former church crypt contains artifacts of the Elephant Man, Jack the Ripper and Florence Nightingale.

A toy store with a century-long history preserves the craftsmanship of playthings of the past.

The signs of a long buried road can still be found hidden beneath a London sewer grate.

This churchyard arbor is surrounded by hundreds of gravestones placed there by author Thomas Hardy.

At the center of London’s oldest roundabout stands an obelisk that was erected in 1771, but spent several decades elsewhere.

A recently restored substation that dates from 1875.

This statue includes the molehill that toppled a king.