Another of California's unused Cold War missile defense complexes has become a graffiti gallery.

Rippling sand dunes frozen in the Arizona rock.

An isolated dive site teeming with cnidarians.

An emerald-green grotto just a short trip from Austin.

An annual festival celebrating Colorado's most famous frozen corpse.

Now abandoned, the first public health hospital in the U.S. saw more than one million immigrants from around the world.

There is nothing like a religious festival celebrated with blow-up sledgehammers.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

The world's largest indoor go-kart racetrack is hiding in Connecticut.

Legends surround this jagged rock formation in the New Mexico desert.

Abandoned anti-ballistic missile base.

The remnants of an early American attempt at missile defense.

The now-abandoned tunnels were built for the transcontinental railroad on the route where the first wagon train entered California.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

One of the most poignant ruins of the Chernobyl nuclear disaster, the local football team's stadium has been quickly reclaimed by nature.

The ghost town left by the worst nuclear disaster of all time is being taken over by nature and urban explorers.

This abandoned Navy base was transformed into an off-grid alternative living community for thousands of people.

A hand-built folk art installation covered with messages of God's love.

Burping, gurgling geothermal mud pots by the Salton Sea.

Abandoned Air Force base that has fallen into disrepair.

Sunset-colored dunes of volcanic ash make taking a poor photo impossible.

Hundreds of drawings left by the land's previous inhabitants remain mysterious.

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

Dozens of lights dangle from the branches of what may be the brightest tree in Los Angeles.