A frozen relic of Seattle's hydroelectric boom is now a teaching facility for future engineers.

A "sinister, whimsical, tacky, and really orange" public art installation hidden under a Seattle bridge.

Fossils, railroads, and waterfalls!

Home to the deepest rift anywhere on Earth.

Historic site where Native American hunters once trapped and killed buffalo.

The only road through the heart of Glacier National Park.

This Yellowstone geyser may not shoot as high as the nearby Old Faithful, but it erupts for considerably longer.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

A beautiful geyser under environmental threat.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

For thousands of years, Native American hunters drove buffalo straight off this cliff in Montana's Yellowstone Country.

These former Cold War launch sites have been preserved for tourists to see where the button might have been pushed.

One man's quest to save his town with a trail of record-breaking sculptures.

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

This public square capitalized on a single Eagles reference to bring some life back to an Arizona town.

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

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

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

This historic national park is covered in the stunning ruins of red rock pueblos.

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

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

A self-built castle made by a mysterious man.

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.