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

The hallowed remains of a 900-year old Ancestral Pueblo great house.

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

This isolated outpost was once the only place to cross the Colorado River for hundreds of miles.

Dramatic river bend surrounds a natural red-rocked pedestal.

Legends surround this jagged rock formation in the New Mexico desert.

A phenomenal assembly of pueblos in New Mexico is the most complete example of ancient ruins north of the border.

One of the most extensive and well-preserved collections of dinosaur footprints in North America.

Red sandstone structures dominate this landscape, which has been inhabited for some 5,000 years.

The cinder cone volcano with a less than complimentary name.

This historic national park is covered in the stunning ruins of red rock pueblos.

The highest point in Arizona is an oddly snow-topped peak within the otherwise arid state.

The wreckage of a deadly bomber plane crash can still be found near an Arizona peak.

This Arizona observatory is famous for investigations into Martian life, and as the place humans first spotted Pluto.

Ancient pueblos built into the base of a natural canyon wall.

The world's only teal arches exist in a city that cares more about its aesthetic than an Instagram influencer.

A spiritual vortex among the red rocks in Sedona.

One of the final grand railway depot hotel complexes is slowly being restored to its former glory.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

These ruins of a pre-Columbian cliff village are among the most beautiful and well preserved in New Mexico.

Every year, festive decorations appear on this juniper tree located in the median strip of a busy highway.

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

A geological mystery on Camelback Mountain.

Hike the unusual hoodoos and rock formations that form this little-known natural wonder.