Native Americans built this circle of stones, which was used to predict astronomical events.

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

A beautiful geyser under environmental threat.

This Yellowstone geyser may not shoot as high as the nearby Old Faithful, but it erupts for considerably longer.

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

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

This quiet park's strange sedimentary spires were named after Kodak's color film.

This rugged area of red rocks and arches is often considered one of the most beautiful places on Earth.

Air Force Academy Chapel made of 100 identical tetrahedrons works to inspire those of all religions.

Strange red rock formations that have been attributed to a higher power for hundreds of years.

There are eight natural springs around town, each with a slightly different taste.

This super steep hike ascends 2,000 feet in less than a mile.

Hidden beneath a bridge, this waterfall is known for the large amounts of graffiti painted on its base.

These faux-cliff dwellings allow visitors to climb around on a replica archaeological site.

Thanks to a quirk of elevation this gift shop produces magic doughnuts that are found nowhere else on Earth.

This naturally-sourced hot spring is now home to a clothing-optional resort.

The highest point in Texas is capped by a big silver pyramid.

An abandoned quicksilver mining town surrounded by the Big Bend parks.

A little stop along the Texas highway where Rock Hudson, Elizabeth Taylor, and James Dean stayed while shooting the 1955 film "Giant."

Mysterious glowing orbs float through the desert night.

This erect, phallic geological spire wasn't always named so domestically.

An experimental, automotive replica of Stonehenge.

Dedicated to the history of the 1,000 nuclear missiles that once covered the Great Plains.

The first declared National Monument in the United States.