This floating cinema brings new meaning to the phrase "going out" to the movies.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

Civil War Fort on an island in the Boston Harbor.

Home to the infamous "Typhoid Mary" and the worst loss of life in New York's history prior to September 11, 2001.

An unusual round church in London with a Templar past.

A 2000-year-old Roman amphitheater lies just below Guildhall Yard.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

Below a historic English market town lies a secret underground city complete with kitchens, laundries, storerooms, and an underground lake.

The world's largest drain sits below the city of Kasukabe, Japan.

The biggest and deepest Cold War bunker open to the public can be found in southeast England.

This attraction was abandoned after the Chernobyl disaster.

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