A world-class observatory in the California desert.

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

Since World War II people have been decorating this stretch of the Yuma desert with signatures arranged out of rocks.

The largest and most well-preserved petroglyph site in the Verde Valley.

An artificial crater field that trained astronauts for lunar exploration.

A nature and cultural preserve named for its multitude of petroglyphs carved by the Northern Sinagua people.

A remote desert lookout offers unparalleled views of the California badlands for those who brave the trek.

An important piece of history from mankind's journey to the moon sits in the lobby of a government science lab.

Inside this garden, visitors are offered a glimpse into how inhabitants of the region survived centuries ago.

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

A mass grave for victims of an airline disaster that led to much-needed safety improvements for commercial flights.

Crafted in 1911, this steam locomotive spent its entire working life in Flagstaff.

The final resting place of the businessman-turned-astronomer who helped discover Pluto stands near his observatory.

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

The cinder cone volcano with a less than complimentary name.

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

Abandoned bridge hidden deep in the San Gabriel Mountains.

This California tree is the single source of the state's entire orange industry.

The sea once considered an ecological wasteland is now called "crown jewel of avian biodiversity" by scientists.

A monument to a one-legged kidnapper, horse thief, and charlatan asks visitors to throw rocks in a pile.

The remnants of a failed socialist commune can still be found just off a California highway.

Erroneously called the world's tallest flagpole, this landmark is devoted to "good neighborliness."

Mexican food and folk art.

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.