Ride the subways of yesteryear.

Tucked in the back of this amazing antique store is an important piece of medical history.

Salute the leader of the proletariat.

This exemplar of modernist architecture is meant to captivate and inspire students of the Cooper Union.

New York City's only preserved family home from the 19th century.

One of the oldest Jewish cemeteries in the city, it is now overgrown with an urban forest.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

Walk into the 19th century without leaving Brooklyn.

This innocent-looking townhome is actually a subway exit.

The mummified heart of Louis XVII, the lost dauphin of the French Revolution.

A decommissioned military complex that's now a modern industrial park.

Repository for more than 22 million pickled specimens.

Architect Le Corbusier built his friend a cubist house to match his impressive collection of cubist art.

The anatomical-pathological collection of a man who changed surgery.

The most visited, and possibly most controversial, museum in Germany.

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

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

Abandoned railway line circling the city of Paris.

The only remaining collection of flayed figures made by French "madman" Honoré Fragonard.

The headless bodies of more than 1,300 guillotined victims of the Reign of Terror are buried here in mass graves.

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

Saintly bones pressed into a wax effigy of a Catholic superstar.

Statue of death tucked in the University of Medicine courtyard.

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