One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

This castle tower in Wales leans at a steeper angle than the Leaning Tower of Pisa.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

This enormous "cloth of the conquest" depicts the Norman invasion of England in mind-blowing detail.

Remains of the artificial harbours invented for the Allied invasion of Normandy can still be seen at sea.

A memorial to the nearly 10,000 American soldiers laid to rest on the beaches of Normandy during WWII.

Yo, Adrian!

The world’s first penitentiary, meant to be humane, drove men insane.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

Elvis's own personal tropical hideaway.

The 10th-tallest pyramid in the world, this former sports arena is now home to a massive Bass Pro Shops store.

This replica of the Greek structure is in the heart of Nashville.

A cemetery for only coon hounds in northwest Alabama.

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

A bizarre roadside attraction and the first instance of miniature golf in the world.

Underneath this water pump, Annie Sullivan helped Keller speak her first words.

A modest Alabama recording studio where some of music’s biggest voices found their sound.

It may look like no more than a full-scale model, but every part of this full Space Shuttle stack had a working role in aviation history.

A propulsion engine testbed that paved the way for the Space Shuttle launch sits without recognition at this rocket center.

Bananas are often left for the first monkey America ever recovered alive after being launched into space.

Once a bustling cotton factory, this early 20th-century building is now home to a thriving artspace.