Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

360° views of the city plus five floors of optical illusions and hands-on science.

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

The oldest surviving bridge in New York City, which reopened to pedestrians in 2015.

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

New York City's smallest piece of private property.

The largest earthwork effigy in the world.

The abandoned husk of a mental institution that failed to save a Jazz Age icon still sits nearly unchanged.

A dilapidated dock tells the story of Titanic's missed arrival.

This collection of illusory paraphernalia has been culled from the history of London's premier magician's club.

A walk-in working camera obscura produces 360-degree live images of the San Francisco coast.

The largest of London's subterranean rivers and once a mad, bad center of London life.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

An abandoned castle owned and ignored by Masons carries a cursed history.

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

The haunting "Hell House Altar" is one of the few remnants of an abandoned college that has been a magnet for local legends.

This abandoned amusement park was built on a site with a dark history.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Resting place of Hollywood's immortals is also site of summer film screenings.

Collapsing castle on the Hudson river was once the storage site of military surplus business.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

Abandoned railway line circling the city of Paris.

A walk through the historic city center, under the streets of Seattle.

A memorial to a shareholder activist feared by CEOs around the United States.