These pretty kitties killed and ate as many as 135 railway workers.

This sky-high radio mast is formerly the tallest man-made structure in the world.

FDR hoped to find a cure for polio in this Georgia town's warm springs.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

See massive fossils that are over 200 million years old in northeastern Arizona.

The world's longest known cave system.

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

World's largest college campus includes a wildlife sanctuary and a former movie set on more than 28,000 acres.

The highest bridge in America was built for an almost unnervingly small amount of money.

These ruins of a pre-Columbian cliff village are among the most beautiful and well preserved in New Mexico.

Legends surround this jagged rock formation in the New Mexico desert.

Now containing the bones of the actual conquistador, instead of someone else.

What was once a unique system of urban elevators is turning into a mechanical ruin.

Constant erosion has created a surreal landscape of bleached and preserved fallen trees.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

Less a museum than a bizarre fantasy world created by artists and engineers.

On any given day this sprawling market houses literally tons of government-regulated gold, gems, and precious metals.

A miniature city built by a single hunchbacked monk.

The highest point in Louisiana, Driskill Mountain at 535 feet above sea level.

A large stone map of Arkansas awaits visitors to its highest point.

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

Monument to the cotton-destroying boll weevil.

As state high-points-by-elevation go this spot is one of the lowest, but for years it was also the hardest to climb.

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