This naturally-sourced hot spring is now home to a clothing-optional resort.

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

A beautiful geyser under environmental threat.

Paranormal experiences in this hotel's room 217 led Stephen King to write "The Shining."

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.

The oldest lighthouse on America's west coast no longer needs keepers, yet they maintain the site anyhow.

Quite simply the largest tree in the world (by volume).

A charming desert roadside bakery that produces 10 times more bread daily than it has residents in its town.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

Towering basalt columns, a creation of fire and ice.

A graceful natural rock formation stands astride the point where the Gulf of California meets the Pacific Ocean.

Crystal clear lake with a shoreline of travertine located in a Colorado canyon.

Wondrous sandstone hoodoos where Native Americans collected clay for pottery, 9,000 years ago.

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

This isolated outpost was once the only place to cross the Colorado River for hundreds of miles.

This rustic old building is said to be the most photographed barn in America.

This former coal gasification plant found a curious second life as a popular public park.

Where Nor'easters go to die.

100-year-old shipwreck you can walk up to at low tide.

A massive sea stack famous for its appearance in The Goonies.

When ecosystems collide in the arid Southwest.

The largest self-built castle in the U.S., six decades in the making.

Chewing gum tycoon's memorial lies perched over wife's botanical gardens on Santa Catalina Island.

A herd of 150 bison live on California's Santa Catalina Island and are at the heart of an ongoing debate between environmental protection and economic expansion.