These colossal desert barcodes have been fine-tuning spy satellites for decades.

Concrete crosses scattered across the Arizona scrubland which were used to align spy satellites.

Where pardoned turkeys once spent their all-too-brief final days.

A relic of FDR's brief foray into utopian urban planning.

The U.S. Army's giant warehouse of war art includes Hitler’s watercolors and Norman Rockwell oil paintings.

The remains of a doomed Antarctic plane, buried beneath layers of ice and snow, await those willing to do a bit of digging.

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

The entire length of the border is marked by a 20-foot-wide slash through the trees.

This sun-scorched lakebed contains samples of half the natural elements known to humankind.

The remains of a failed attempt at medieval nerdery are hidden deep in the woods of Virginia.

On the Oregon coast there is a natural hole that seems to be draining the sea.

The half-mile long structure is so impressive, it even shows up on satellite images.

Monument to a brutal, ineffectual US bombing campaign and a sobering reminder of the human cost of the Vietnam War.

Florida’s half-sized replica of the Vietnam Veterans Wall.

Proto-CIA agents trained with grenades in the sand traps and fired machine guns from the fairways.

The vertical-axis windmills of ancient Persia have been grinding flour for 1,000 years and counting.

The remnants of an early American attempt at missile defense.

Museum dedicated to overthrowing the Soviets, complete with diorama of Soviets being beaten to death with shovels.

The world's foremost museum dedicated entirely to the abacus.

The largest radio telescope in the world searches for extraterrestrial life from the remote limestone peaks of southern China.

This 29-ton granite ball spins around at the slightest touch thanks to a scientific phenomenon.

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

This massive swimming pool is the high tech home to the human-powered submarine races.

A mammoth pair of Civil War artillery guns abandoned out in the forest.