In Twickenham sits a small whitewashed castle that inspired Mary Shelley's 'Frankenstein.'

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

World's first "penitentiary," meant to be humane, drove men insane.

Mural made of 100,000 pieces of hand blown glass, and until recently, the largest glass mural in the US.

New Orleans' famous cemetery, located on the site of a former race track.

This historic Boston building has gone from personal estate to porn theater and back again.

The history of the tea trade is told in bas-relief on this historic pair of Boston doors.

This giant Boston statue of Mary is standing on a globe to show her power over the universe.

The oldest surviving wood-frame building in North America is still in the family.

Venice's "Island of the Mad."

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

Built to repay the sins of the father, this church is home to one of the most valuable works of Western art.

Now an entertainment complex, the Lingotto building was once an avant-garde auto factory with a test track on the roof.

This hill made entirely of ancient Roman jars was simply a garbage dump to the people of the time.

World's largest precision optical instrument used to detect Einstein's elusive gravity waves.

One of Frank Lloyd Wright's final works was this UFO church.

Tour the luxe "glass cage" that inspired and unnerved the architecture world upon its debut.

Museum mostly in name, and only a restaurant depending on the day, this place could only exist in Marfa.

New England's tallest light house stands on an island with a history of cannibalism and death.