The second-largest ceremonial mound in the United States is an artificial hill that is loosely shaped like a pentagon.

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

Rusty red sands line the shores of this Canadian Province.

The self-made house sculpture of an outsider artist who named himself "Chief Rolling Thunder."

Local history museum with mammoth bones and an old myth about local giants

Singing sand that stands as the final remains of an ancient lake.

A petroglyph map of the upper Snake River carved by prehistoric hunter-gatherers.

A small section of Boise, Idaho maintains the unique culture and traditions of the Basque people.

Boise State's stadium was the first non-green football field in the world.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.

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

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

Oregon's unexpected high desert, displaying layers of time in a colorful show.

The largest earthwork effigy in the world.

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

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

A beautiful geyser under environmental threat.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

A 6-mile-long lake created by an apocalyptic seismic event and the deadly chain reaction that ensued.

Natural sonic phenomenon comes with a grisly legend of murder and blood.

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

These black pillars of volcanic basalt seem to call mountain climbers with an unbreakable siren song.

Jail from the 19th century that was built by inmates.

Rare and gorgeous birds abound in this protected wildlife sanctuary.