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

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

An urban laboratory.

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

The fading, forgotten remains of a once bright and booming factory.

Limestone caves with spectacular showcase chambers.

A spiritual vortex among the red rocks in Sedona.

The story of Two Guns, Arizona could easily be described as a Shakespearian tragedy on Route 66.

America's only nuclear missile silo open to the public.

Ancestral Puebloan ruins, natural arches, and box canyons abound in this seldom-visited corner of Monument Valley Navajo Tribal Park.

A stealthy Apache hideaway that became the haunting site of a mass grave.

An homage to everyone's favorite prehistoric cartoon family.

An arsenic-filled pool in the Grand Canyon takes on the appearance of a giant, overflowing pumpkin.

A reproduction of earth's many biomes.

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

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.

This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.

Dramatic river bend surrounds a natural red-rocked pedestal.

Rippling sand dunes frozen in the Arizona rock.

A little slice of Florida face-in-a-hole kitsch, unexpectedly located in a small New Mexico town.

Thousands of mounted insects, and some live ones, hide within an otherwise ordinary shopping mall.

A natural formation that resembles a camel resting in the New Mexico desert.

A somber monument commemorates the site of a Native American reservation marked by suffering.