These mysterious ancient stone spheres were created by a civilization lost to time and are now mostly lawn ornaments.

This Costa Rican topiary park is a surreal garden of unearthly delights.

This neon blue river gets its color from a unique mix of bacteria and volcano minerals.

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

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

A Tucson museum and performance space full of found-object movable sculptures.

This southwestern historic site was designed and built by an artist who wanted his work to "feel at home."

A reproduction of earth's many biomes.

The state's only comprehensive museum dedicated to the mineral that defined its history and economy.

Outsider Art Community.

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

An abandoned facility that has become a place of ritualistic satanic worship, or so rumor has it.

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

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

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

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

An urban laboratory.

A self-built castle made by a mysterious man.

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

Thousands of Mexican Free-Tailed Bats soar around an abandoned storm drain at sunset each summer.

In this small Phoenix taxidermy emporium, you can find everything from a squid in a jar to a freeze-dried toad.

A well-preserved medieval village nested on a rocky outcrop and surrounded by a network of cliffs, natural bridges and canyons.

No one knows who created the statues or if they are arranged properly—let alone the artwork's real name.

The vast, legendary catacombs hold secrets much stranger than stacked bones.