A subterranean world of tunnels links several buildings of this rare 19th-century asylum.

Colorado Boulevard’s historic bookstore, operating since the bustling city of Pasadena was merely some orange groves and a few ostrich farms.

A huge musical sculpture and other art installations on the National Oceanic and Atmospheric Administration grounds.

Crypt mausoleum in cathedral's basement contains relics of third century Roman martyr, Saint Vibiana.

A walk through the historic city center, under the streets of Seattle.

The historic bar where local ship captains, traders, and gold miners would come together to do business a century ago.

Abandoned bridge hidden deep in the San Gabriel Mountains.

Trails through lava-carved tube-caves display sparkling bacteria and a rich history.

Canyon walls shrouded in ferns.

This abandoned boat was left in place thanks to its rotting beauty.

A grove of "candelabra redwoods" deep in California's Lost Coast.

A trash dump made beautiful by nature's power.

The mysterious round rocks of Schooner Gulch.

Graffiti-covered ruins that were once part of a farm owned by a mental hospital.

Rusty pieces of metal jutting out of a breakwater are all that's visible of the 12,500-ton ocean liner that capsized just off the beach.

Colorful Native American paintings are hidden within this small cavern.

This sign designates the road that leads to the infamous Area 51.

Water of undetermined depth has attracted rare fish and cult leaders alike.

Back in 1952, you could get a mushroom cloud chaser with your atomic cocktail.

One of the ghostly stops along Route 66.

This arid landscape was once a lush wetland. Today, it's a paleontological site filled with fossilized mammoths, sabertooth cats, and more.

A volcanic tunnel illuminated by natural skylights offers a shaded respite from the desert sun.

This 1920s masterpiece of French Quarter architecture hides a secret tunnel used by Albert Einstein.

Every weekend, the parking lot of this Buddhist temple turns into a Thai street-food paradise.