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

Walk through the actual strap iron cells and solitary chambers of Arizona Territory’s first prison.

Stairs often replace streets on the steep slopes of this old mining town.

Limestone caves with spectacular showcase chambers.

The biggest solar telescope in the world helps reveal the secrets of our sun.

A stone pillar marking the location of the westernmost battle of the American Civil War only honors one side of the conflict.

One of the largest open-pit copper mining operations in the entire country.

After a short-lived attempt to bring America in line with the rest of the world, this road was left in metric.

America's only nuclear missile silo open to the public.

Legend says train robbers stashed their gold within the depths of this unusual cave.

The world's largest military aircraft cemetery.

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.

An off-the-beaten path cave with an underground lake.

A reproduction of earth's many biomes.

Miniature art that tells an enormous story.

Religious statues built because of one man's bargain with God fill this peaceful sculpture garden.

Sleep where gangsters fell amidst smoke and flame, with nary a bullethole to show for the legendary struggle.

In Tucson a giant metal snake helps pedestrians cross a busy highway.

A rare wayfinding portmanteau of “Street” and “Avenue.”

This iconic 1958 tower welcomes air travelers to Tucson with neon-lit letters and architectural style.

Despite a recent paint job, the factory still sits empty.

Run by members of the Tohono O'odham Nation, this community farm nurtures traditional desert cultivars.

This church on a Tohono O'Odham reservation has stood since 1797.

A natural history wunderkammer in the middle of the desert.