A castle built by an eccentric medieval enthusiast in rural Ohio.

The largest earthwork effigy in the world.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

Speak to a companion on the other side of the room loud and clear through this architectural anomaly.

What was once a presidential estate is now an exotic menagerie and home to the Budweiser Clydesdales.

Even with its slightly risible name this colossal cross is still able to inspire awe.

Standing in a state of "arrested decay," this ghost town allows for a detailed peek into Gold Rush life in an unusually harsh climate.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

Stepping away from the glitz of mobsters and casinos to learn about the other history of Vegas.

"Only the devil could play golf here."

Millions of years of oxidation make a drive down this winding Death Valley road surprisingly colorful.

The lowest point in North America is home to an undrinkable pool surrounded by fields of geometric salt flats.

Dyed by iron oxide over centuries, these sandstone rocks rise thousands of feet into the sky.

The drama of nature in full effect in this Nevada State Park.

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

A phenomenal assembly of pueblos in New Mexico is the most complete example of ancient ruins north of the border.

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

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

Hidden inside this Arizona fast food franchise is an in-depth exhibit on the famed WWII counterintelligence program.

An antique narrow gauge railway line still running through the Colorado and New Mexico mountains.

Inspired by a music box, a small town Vietnam vet carved an entire carousel full of animals by hand.

When ecosystems collide in the arid Southwest.

The spot in the Mile-High City that's exactly 5,280 feet above sea level (at least for now).