Legend says it was constructed with the destroyed pillar of an ancient Greek Temple.

Gladiators once walked this ancient, subterranean passage.

Where commuters walk through remnants of an ancient Greek necropolis.

A spectacular remnant of an Adler and Sullivan masterpiece that was destroyed in 1972.

This alley in downtown Chicago held the bodies of over 600 people after the fateful Iroquois Theatre fire.

The beloved home to all publications indie, erotic, and punky.

These abandoned grain silos and tunnels are an urban exploration dream.

A monument to the art of slicing people open.

This building contains a door only used by members of the royal family.

This small, round building is the entrance to a bomb shelter built in anticipation of World War II.

Tucked away behind the mansions of Mayfair, this picturesque garden is a hidden London treasure with a spooky past.

A building that survived WWII, possibly on the virtue of its name alone.

William Smith's iconic "map that changed the world" is hidden behind a curtain in the Geological Society building.

A series of carved figures that scandalized British society.

A gruesome and mysterious ancient sculpture of a pagan deity from the Roman occupation of Celtic Britain.

This Underground station has been a popular filming location for decades, even before it closed.

This unassuming alcove in London’s famous Tower Bridge once served to capture, store, and display dead bodies from the River Thames.

The pockmarks across the building's facade are remnants of the Blitz.

This medieval church tower has maintained its clockworks since the 16th century.

A monolithic monument in Greater London.

A mysterious shape catches the eye in this 16th-century painting.

The bronze uniforms commemorate the vital role of women during World War II.

A plaque marks the underground site of one of London's "lost rivers."

This educational institution and reference library specialize in the psychic arts and mediumship.