This now-deactivated naval base defended the Florida coast for centuries.

Constructed in 1892, this Hinesville jail is now an art gallery.

One of the largest-ever mental hospitals now sits abandoned, surrounded by 25,000 unmarked graves.

A white oak with property rights.

This distinctive Crescent City tradition dates back to the days of horse-drawn carriages.

By day this New Orleans square is for pedestrians, but by night it is a kingdom of kittens.

A historic Civil War estate-turned-museum looks back on the Confederate States of America.

These wire animal sculptures commemorate the exotic inhabitants that once called the Tower of London home.

A mysterious suspended hand greets unsuspecting visitors at the Tower of London.

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

Tucked away in the Tower of London is the weapon once used to execute high-profile prisoners.

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

A discarded movie prop that was the original monolith for "2001: A Space Odyssey."

An architectural oddity hides in plain sight on this iconic London bridge.

Where condemned pirates met their grisly end at the gallows on the River Thames.

This striking observation tower shaped like a spinnaker sail is the newest icon in historic Portsmouth.

This colossal war machine is now a living museum dedicated to underwater warfare.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

This stone tower was built to protect Crete from incoming pirates.

This tiny cafe is one of the last meeting places of its kind, allowing revolutionaries a place to plot.

One of the largest ochre quarries in the world, hidden in a limestone landscape.

This modern museum of Mediterranean culture is surrounded by a surreal concrete honeycomb.

This historic island prison holds one of the dungeons from the Count of Monte Cristo even though it is a work of fiction.

If all members were present at the table, a sixth of the world's wealth would be under the same roof.