The oldest pictographs on this decorated rock formation in California's Carrizo Plain date back as many as 4,000 years.

An abandoned facility that has become a place of ritualistic satanic worship, or so rumor has it.

This 18th-century project to build the world's tallest gravity dam was never completed.

This comprehensive collection features Native American artifacts dating back centuries.

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

An old saloon in the West filled with history, and according to some, a few dozen ghosts.

Some of the tallest ancient American ruins continue to inspire awe and curiosity.

Limestone caves with spectacular showcase chambers.

With its peeling paint and faded sign, this theater-turned-recycling plant is a nostalgic relic of 1950s Americana.

Inky sludge oozes to the surface of this beach thanks to a rare natural tar seep.

A 19th-century Baja cantina that many say is the birthplace of the margarita.

The beauty and the beast of hydraulic mining is on full display at this California Historic State Park.

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

A massive volcanic plug is now a protected area that hosts a number of bird species.

An alley covered with 20 years of bubble gum.

Factory that once supported an entire company town of 350.

Coastal dunes, site of buried Egyptian movie set and former utopian colony.

A Mysterious Masonic tomb in San Luis Obispo.

A hotel and restaurant serving as the mecca of kitsch.

The last bastion of Roman presence north of the Alps looms over a German town.