Standing guard on top of an old, vacant ice cream shop.

Controversial tribute to the heavyweight champion boxer who grew up in Detroit.

Enormous small-business mecca in the Midwest, serving dozens of artists.

The concrete shell of an industry giant remains as a playground for graffiti artists, auto scrappers, and paintball warriors.

The old Niles Canyon Aqueduct in the San Francisco Bay Area is a bemusing and secret trail through nature for wayward travelers.

A Roman-inspired temple once controlled half of San Francisco's waters.

The world's first permanently occupied mountain-top observatory continues to report on the stars.

Apple memorabilia in an undisclosed warehouse, hidden for undisclosed reasons.

From the Difference Engine to the Cray-1, all under one roof.

San Francisco Bay's ghost town.

This giant shopping mall still holds signs of its automotive past.

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

A giant chess set, minus the psychedelic drug trip.

The headquarters of a secretive order is also a beautifully-designed park.

An extensive collection of ancient Egyptian artifacts and mummies.

This failed condo development was reborn as a street art hub.

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

One part antique store, one part curiosities hodge-podge.

Home to the largest urban bat colony in North America, estimated at 1.5 million bats.

Free public park and gardens filled with peacocks and peahens.

A grove of colossal man-made flowers built to collect the sun's rays.

Turning night into day in Victorian-era Austin to thwart a serial killer.