The maximum security facility was once thought to have "the bloodiest 47 acres in America."

Giant granite rocks standing end-to-end like a train of circus elephants.

A geological oddity formed by two rivers carving out a mass of limestone on both sides.

Erosion and time have created a naturally-formed water park.

400 million-year old limestone caverns nestled in the Ozarks served as shelter and a hideout for cultures throughout North American history.

Curious cave that stays a cool 56 degrees all year long.

The world's largest man-made underground caverns offer unparalleled underwater wonders.

The "World's Largest Underground Business Complex," a 55,000,000-square-foot city underneath Missouri.

Once an ambitious nature spa, these forest ruins now provide a serene monument to failure.

This abandoned prison castle has become an imposing gallery of graffiti art.

European castle ruins in an American state park are actually the product of death and grief.

A Jurassic artscape composed of transmission casings and other mechanical parts.

Cannon designed to fire an atomic warhead.

Home of mutant livestock.

One of the stops along the fateful journey of the Donner Party.

A steeple that now houses a small church.

Once an ancient sea, this landscape of rocky ravines is filled with the fossils of ancient marine life.

This mid-19th-century dugout was once home to a Swedish family as they erected their homestead.

This three-dimensional brick mural is the longest of its kind in the United States.

Hundreds of samples of "Devil's Rope" hide in a defunct vintage elevator.

This statue is an ode to an iconic roadside advertisement popularized during the 1970s.

This tiny old water tower once doubled as a makeshift jail.

A museum documents the development of the invention that tamed the Wild West.

This 100-foot tall bluff located in the western plains of Kansas overlooks a massive reservoir.