An improbable sinkhole in the sediments flanking the Beaver Dam Mountains.

At certain times in the fall and winter, the sunlight makes this natural sandstone arch glow.

A short interpretive trail about one of the first human cultures in North America.

This small museum is dedicated to the study of coprolites, or fossilized poop.

This open-pit mine is now an abandoned symbol of Bisbee's copper-mining heritage.

An assortment of armored tanks and Howitzer cannons in the middle of the Sonoran Desert.

The exit of the largest prisoner-of-war escape attempt on American soil during World War II.

This rusted car found in Petrified Forest National Park's Route 66 exhibit may be the most photographed abandoned car in the country.

The former home of the army detachment that captured Geronimo.

Archaeologists believe this panel of petroglyphs depicting descending sheep and other figures in Glen Canyon are 3,000 to 6,000 years old.

The Grand Canyon’s original airport, which once welcomed pilots like Amelia Earhart and Charles Lindbergh, lies abandoned.

A century-old miner's quarters turned mansion.

This sinkhole in the Arizona desert is filled with carbonated, arsenic-rich water

During World War II this was the site of an "honor camp" used as a prison for draft dodgers, Native American conscientious objectors, and Japanese-Americans—including a man who brought his case against the camp to the Supreme Court.

This memorial includes fragments from one of the greatest tragedies in United States history.

These petroglyphs created by ancient Arizonians have withstood centuries of exposure to the elements.

In 1975, a forestry worker in Arizona claimed to have been abducted by a UFO.

One of the best-preserved ghost towns in Arizona speaks to the difficulties of establishing mining towns in the 19th century American West.

An excursion train traverses a picturesque red-rock canyon along the Verde River.

The stone circle honors the 19 firemen who perished during the Yarnell Hill Fire.

Two geoglyphs that are truly unique to North America.

A stone pillar commemorates the surrender of the extraordinary Apache leader.

This once-booming Gold Rush town is now home to a herd of feral donkeys.

A strenuous, unofficial trail leads to spectacular views in one of America's most remote national monuments.