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.

Carved by a waterfall in a hard-to-reach rock formation, this heart-shaped rock has inspired romantics for decades.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

A trash dump made beautiful by nature's power.

Under the right circumstances, this waterfall in Yosemite briefly turns a luminescent fiery orange.

A huge musical instrument played by the ocean.

A wild trout fishery in Arkansas.

The only diamond mine in the world where you can keep what you find.

The Old Mill shown in the opening credits of “Gone With the Wind” is actually fairly new, and was never a mill at all.

The final remnant of the Arkansas zinc industry is this historically protected ghost town.

Twenty-year effort to raise a castle using tools and techniques from the 13th century is now abandoned in the Arkansas woods.

This futuristically sylvan church is a glass-enclosed marvel of modern architecture.

The largest natural travertine bridge in the world is nestled in a small canyon in central Arizona.

This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.

Limestone caves with spectacular showcase chambers.

A stealthy Apache hideaway that became the haunting site of a mass grave.

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

Dramatic river bend surrounds a natural red-rocked pedestal.

Most-visited and most-photographed slot canyon in the American Southwest.

Rippling sand dunes frozen in the Arizona rock.

At 238 feet above the bottom of a gorge this span is known as the biggest thrill on the road to McCarthy.