New York City's smallest piece of private property.

A dark, dank room in subterranean Manhattan was the site of a ghastly murder.

Have a steam and some blini at this cafe in a century-old bathhouse.

This beautiful building in the heart of Manhattan's Financial District was empty for decades.

This museum chronicles the history of a leprosy quarantine hospital that then became a refuge.

This sculpture may be the only known depiction of a man who helped finance the American Revolution and inadvertently created the dollar sign.

A mysterious find dredged from Louisiana waters.

An unremarkable wooden wheel built into the side of one of Rome's oldest hospitals was part of a policy to reduce infant exposure.

This hidden alley near the location of Rome's first theater was the site of a curious miracle.

The underground sanctuary of a mysterious ancient cult.

In Rome’s Jewish ghetto, a 200-year-old bakery still makes the neighborhood’s historic sweets.

In the early Roman Empire, people deemed traitors and criminals were tossed to their deaths from this rock.

This statue is the only female representation of Rome's "talking statues."

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

This ancient market is often referred to as the oldest shopping mall in the world.

A forgotten "city of water" underneath the famous Trevi district.

An alchemist's "magic door" stands in the middle of a Roman park.

Architectural monsters are devouring this palace's every door and window.

This Roman arch marks the location of an ancient gate at one of the Seven Hills of Rome.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

Ancient ruins hidden underneath a modern luxury hotel.

A historic canal winds through a unique, swampy landscape.

A preserved factory in the "Home of the Carrousel" is now a museum dedicated to the classic wooden ride.