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

Come for the speed, leave in love with the desert.

A well-preserved Ancestral Puebloan ruin tucked beneath a desert cliff.

This geothermal hot spring hides beneath a slowly growing mineral dome.

The hike through a narrow river flanked by the 2,000-foot-tall walls of Zion Canyon is one of the best in the world.

Here, at the "world's longest art gallery," you'll find forty miles of ancient petroglyphs and pictographs.

It takes a nine-mile hike to reach these hot springs, but weary hikers are rewarded with stunning views and a warm soak.

This once-popular otherworldly landscape was formed by one of the largest volcanic eruptions in history.

Despite being one of the most photographed vistas in the Rockies these twin peaks are rightfully known as the "Deadly Bells."

The superstar of Cold War nuclear bunkers has been featured in countless films but is now barely operational.

The highest bridge in America was built for an almost unnervingly small amount of money.

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.

An enchanting natural wonder in Puerto Rico's Camuy River Park.

Ride a boat through this magnificent underground world, which now doubles as a theater.

148 feet long and in the middle of a verdant forest.