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

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

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

This abandoned horse racing track was an exercise in hubris from its inception.

Opinions differ as to whether this Arizona tree was actually used as a Wild West jail, but that hasn't stopped the town from capitalizing on it.

Some of the tallest ancient American ruins continue to inspire awe and curiosity.

On the outskirts of a reborn ghost town, a decaying post office remembers the bad old days.

Once the product of an inexplicable gold strike, this ghost town is now home to one man and his love of classic machines.

A self-built castle made by a mysterious man.

A Wild West jailhouse that slid down the mountainside.

A spiritual vortex among the red rocks in Sedona.

A mysterious "wedding cake" castle in the middle of the urban desert.

A museum and tribute to a brave profession.

A geological mystery on Camelback Mountain.

A towering bronze statue memorializes the founding father of postwar American conservatism.

An urban laboratory.

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

The massive, incredibly rare instrument is over 11 feet tall with a range so deep it goes lower than humans can hear.

This collection of Wild West movie memorabilia also claims to hold some secrets of the Lost Dutchman's mine.

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

Over 60 chemical plants and oil refineries sit in a 15-mile-wide section outside town.

This seemingly cursed monument is dedicated to one of Canada's great war heroes.

These locks on North America’s oldest canal are named after a porcine rock formation.

This mill on Lake Erie appears to shrink as a viewer approaches thanks to an optical illusion.