The remains of Crystal Palace Great Exhibition of 1851.

A collection dedicated to the treatment of disease, held in London's oldest hospital.

A historic London pub with prison cells in the cellar and a "spy room" on the second floor.

Rebuilt remains of a temple to Roman god Mithras.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

A subterranean ice warehouse that has lain hidden beneath central London for over a century is now open to the public.

One of the largest pieces of scientific equipment ever carried on a NASA space shuttle sits in a Chicago alley.

An exhibit of items from the mental institution where Mary Todd Lincoln lived after her son conspired to have her committed.

A historic and oft-filmed prison stands in a Chicago suburb.

A one-armed veteran of the Battle of Waterloo lies in a cemetery for one in the middle of a Chicago scrapyard.

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

A plaque marks a former safe house on the secret route, now hidden next to a McDonald's.

Arguably the best example of an authentic Dutch windmill in the United States, rivaling its counterparts in the Netherlands.

The multinational Burger King chain is banned from operating within 20 miles of a family restaurant filed under the same name.

A river with some unusual, and occasionally dangerous, habits.

The final resting place of up to 6,000 Confederate soldiers, the largest mass grave in the Western Hemisphere.

A notorious Route 66 eatery once frequented by Al Capone.

Cold War missile launch site which has been converted to a public park.

Quirky water tower advertises the long-gone Brooks Tomato Products Co.

The legacy of an unsolved, gruesome murder rests beneath the spans of this historic bridge.

A small abandoned and abused cemetery that has become a magnet for ghost hunters.

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

Even with only two residents and one building, this tiny Illinois town is famous for its burgers.

What was once the second largest steel mill in the US is now a sprawling complex of modern ruins.