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

These unusual rooms on wheels are holdovers from the 1960s.

At Washington's Dulles Airport is a satellite museum (no pun intended) with three quarters of a million square feet of aircraft history.

The graveyard holding the remains of George Washington's slaves was forgotten for nearly 200 years.

Thomas Jefferson's estate is home to hundreds of varieties of historic fruits and vegetables.

Forget Hollywood, one of the biggest stars in the world can be found in Roanoke, Virginia.

At 207 feet, one of the world's longest continuous escalators.

This pre-Revolutionary War grist mill ground corn and flour for soldiers in seven American wars.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

A 300-yard long natural tunnel runs through a ridge deep in the Appalachian Mountains.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

So many migrating birds roost on the bridge, it has a special summer speed limit.

Down the road from where the Wright brothers lifted off is another flight tribute practically hidden from sight in the woods.

The Cadillac Ranch for monster truck aficionados.

This winding road of 318 curves is a must-visit for (careful) motorcycle and sports car enthusiasts.

This shifting North Carolina sand dune is an odd little desert surrounded by oceanic forest life.

Beautiful Gothic-inspired lighthouse stands out among the run-of-the-mill striped fare on Bodies Island.

The only known Futuro house in North Carolina sits along a stretch of desolate highway on the Outer Banks.  .

One of the best places to see feral Colonial Spanish Mustangs in the United States.

The highest point in Tennessee, Clingmans Dome bears witness to the ravages of one type of insect.

Home to items never before seen by the public.

Hollywood's most famous landmark, the "temporary" sign that has stood for decades longer than intended.

Elevated freight railway turned wildly successful urban park.

It should come as no surprise that the best view of the Hollywood sign is from Batman's lair.