A breathtaking array of ancient Pueblo structures and artifacts counterintuitively preserved by neglect.

The largest self-built castle in the U.S., six decades in the making.

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

Wondrous sandstone hoodoos where Native Americans collected clay for pottery, 9,000 years ago.

Crystal clear lake with a shoreline of travertine located in a Colorado canyon.

The crumbling structure is a rare surviving relic of the area's bygone mining industry.

A small town built on an abandoned airfield has former runways as streets and a bar and grill in an old airplane hangar.

Population: 1.

A popular rock that acted as a waymarker for American pioneers.

One of the largest collections of wildlife art in the United States, built into the side of a cliff in rural Wyoming.

This mining town boomed in the Atomic Age when uranium was gold, only to be abandoned when the industry collapsed.

This prison-turned-museum is a remnant of the Old West's grizzly, violent past.

One of the smallest towns in the United States.

A miraculous natural phenomenon known as "the spring that breathes."

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

The first declared National Monument in the United States.

This limestone outcropping was once a ceremonial site for ancient Native Americans.

This tiny 19th-century tunnel was built so a man could move his cows from one field to another.

This park contains one of the largest concentrations of cedar glades, a unique and rare ecosystem.

This large cave is a summer home to thousands of bats and has a rich history dating back to prehistoric times.

Abandoned for 60 years, this submerged bridge was completely forgotten until the lake was drained.

Hiding behind a grocery store is a spectacular cavern carved as part of an old limestone quarry.

This former maximum-security prison is creepy, sobering, and supposedly haunted.

In one of America’s oldest mountain ranges, a long-awaited section of a scenic highway is now open to the public.