Thousands of pieces of art have been carved into the rock at the site of an ancient volcanic eruption.

A multi-storied adobe complex has been inhabited for more than a thousand years.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

A nature and cultural preserve named for its multitude of petroglyphs carved by the Northern Sinagua people.

A mysterious spirit totem at the edge of Navajo lands.

Bootleggers ran booze beneath this building before (and after) Route 66 appeared beside it.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

These unique volcanic rock formations offer the perfect opportunity to camp and hike.

"X" marks the spot of an echo chamber in the middle of a plaza.

This immigrant bridge once spanned the Thames but is now a fixture of an Arizona city.

This huge dam across the Colorado River caused an armed standoff between two U.S. states.

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

Ute tour guides have been sharing the ancient dwellings and rock art inside this large park with visitors for more than 40 years.

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

Possibly the world's only drive-in movie theater with an attached motel.

Two tall rocks sit at the center of this site, once the home of a large Ancestral Puebloan community.

No one knows exactly how deep the world’s deepest geothermal hot spring is.

The 7,000-foot finish line of America’s first Olympic Trials marathon.

This small piece of railroad history sits behind the parking lot of a chain grocery store.

This volcano rises like a giant anthill from the plains below, with a road spiraling up to the rim.

The final resting place of the most famous outlaw in the Old West.

The Grand Canyon of Texas.

The final resting place of the living embodiment of the famous Forest Service symbol.

Twice a year, visitors can tour the desolate site that birthed the Atomic Age.