This striking public art installation is suspended above a public park, designed to gently move in the breeze.

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

This immigrant bridge once spanned the Thames but is now a fixture of an Arizona city.

The world's largest military aircraft cemetery.

Limestone caves with spectacular showcase chambers.

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 artist James Turrell is repurposing an extinct volcano crater as an observatory to experience the cosmos.

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.

See massive fossils that are over 200 million years old in northeastern Arizona.

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

A reproduction of earth's many biomes.

The installation’s official name, “You Who Are Getting Obliterated in the Dancing Swarm of Fireflies,” says it all.

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

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.

Most-visited and most-photographed slot canyon in the American Southwest.

Rippling sand dunes frozen in the Arizona rock.

A high school astronomy enthusiast designed this model of our solar system to be traversed on foot.

Don't be a grizzly man. Get personal with Alaska's wild bears from the safety of this conservationist camp.

Internationally recognized group that works to protect the wolf and educate the public about its plight.

An Alaska livestock farm devotes itself to harvesting wool from creatures that once ran with mammoths and sabertooth tigers.

Low tide reveals 8,000-year-old rock carvings in Southern Alaska.