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

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.

A planet-hunting astrograph built in the 1920s to seek out the so-called "Planet X" beyond Uranus.

Every Christmas, one Arizona city makes the most of its dry climate by creating an arid desert tannenbaum.

A secret fresh water spring for animals and humans alike hidden along the most famous road in the United States.

This once-booming Gold Rush town is now home to a herd of feral donkeys.

All of the 20 occupied houses in this mostly abandoned town feature some curious display of junk art.

A Wild West jailhouse that slid down the mountainside.

Inside this store, a mysterious statue draws visitors from the world over.

This small, unassuming street is now a canvas for color and creativity.

A geological mystery on Camelback Mountain.

The biggest solar telescope in the world helps reveal the secrets of our sun.

A reproduction of earth's many biomes.

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

These free-roaming horses were once destined to disappear from the land.

This 40-room dwelling tucked within a cliff was built by the basin's prehistoric residents.

You don't have to visit the deep blue sea to see these majestic creatures swimming wild and free.

All that remains of this Massachusetts town, demolished in the name of progress, is a stone marker.

The largest body of water in Massachusetts annihilated four small towns just to slake Boston's thirst.

Three prestigious academic collections come together to create a world-class natural history museum.

Impossibly life-like natural history models created out of glass by a father and son.

This cemetery served as the only official burial grounds in Cambridge for nearly 200 years.

The statue of John Harvard isn't actually John Harvard—or even, technically, the founder of the school.