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

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

This otherwise unremarkable ski town building marks the site of Butch Cassidy's first robbery.

This spectacular track has run continuously since 1882.

An eatery for UFO seekers on the Extraterrestrial Highway.

Mysterious meeting place for UFO hunters near Area 51.

In the middle of an extremely unforgiving and desolate high desert is the most secret military facility in the world.

"Only the devil could play golf here."

The lowest point in North America is home to an undrinkable pool surrounded by fields of geometric salt flats.

This crumbling Death Valley mining complex was known for its use of giant, 20-mule team wagons.

The rocks in this arid basin leave trails of movement behind them.

Travelers leave tea kettles in a remote part of Death Valley as part of a mysterious, decades-old tradition.

An abandoned Jazz Age dream home and con man's hideout in Death Valley.

A charming desert roadside bakery that produces 10 times more bread daily than it has residents in its town.

Once thought to be the oldest living tree in the world, Methuselah was germinated before the Egyptian pyramids were built.

Hidden inside this Arizona fast food franchise is an in-depth exhibit on the famed WWII counterintelligence program.

The eroded core of an ancient volcano is now accessible by a short hike.

Witnessing the might of this dessert-colored desert waterfall is a rare, powerful treat.

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.

An artificial crater field that trained astronauts for lunar exploration.

An urban laboratory.

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

A once popular resort—said to be the vacation spot of gangster Al Capone—now remains abandoned in the woods of Arizona.