The Empire Mine is "one of the oldest, largest, deepest, longest and richest gold mines in California."

A miraculous natural phenomenon known as "the spring that breathes."

The remote outlaw hideout of Jesse James, Butch Cassidy, and the Sundance Kid.

A beautiful geyser under environmental threat.

The first declared National Monument in the United States.

Touch an actual dinosaur bone at this eclectic trove of Rocky Mountain treasures.

The residents at this Yellowstone wildlife park will certify your cooler as "bear-proof."

The only road through the heart of Glacier National Park.

This oddity shop contains everything from antique tools to a human skeleton.

Home to a timed geyser created by complete accident.

This historic Idaho island is home to a strange timeshare museum, a homemade mini-golf course, and an outhouse named Aunt Fanny.

The mayor made the declaration in 2004.

Sweet Willy, at 30 feet tall, is the world's biggest beagle.

Largest collection of mounted dinosaur specimens in the world.

Despite its name, this route in southern Utah offers a heavenly day trip.

A replica that won't float away.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

Once a menacing challenge for trailblazers, this trail is now the most scenic drive in Utah.

This concert pavilion on the shore of the Great Salt Lake has been destroyed by fire, water, and disinterest but keeps coming back.

This rugged area of red rocks and arches is often considered one of the most beautiful places on Earth.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

One of the world's oldest and most massive living organisms is a grove of quaking aspens.

Here, at the "world's longest art gallery," you'll find forty miles of ancient petroglyphs and pictographs.

Nearly 300,000 acres of wildlife, natural splendor, and a hidden ghost town have been designated a national monument.