The viewpoint for this attractive, off-the-beaten-path waterfall is reached by a paved, wheelchair-accessible trail.

This hiking/biking/horse trail along an old railroad grade features trestles, tunnels, and a roadless stretch through the scenic Susan River canyon.

This concrete tangle of square pipes has stood as a proud thorn in the city's side since the '70s.

A huge musical instrument played by the ocean.

A promotional sun clock on the site of San Francisco's great raceway.

Radioactivity still cause for concern at this urban explorer's paradise.

A breathtaking 19th-century trail overlooks Lake Tahoe.

A natural sandstone bridge hidden in the Sewanee forest.

This cabin once belonged to one of California's original settlers.

Here, visitors can swing with the waves of the Pacific Ocean.

California's own majestic geyser is powered by a subterranean volcano.

This graffiti-covered bridge is the quintessential vision of a place for disillusioned youth to escape the complexities of burgeoning adulthood.

A train tunnel that was made obsolete by the dam it helped create.

A fire lookout atop a glacial pinnacle is reached by climbing three vertiginous flights of stairs.

An abandoned Cold War missile radar site.

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

San Francisco Bay's ghost town.

Law-protected wreckage serves as a peculiar memorial for an almost forgotten World War II tragedy.

This enormous World War II relic is one of the largest wooden structures in the world.

Hidden beneath a lake for decades, this brutalist mine has now emerged from beneath the receding waters.

Once America’s most beautiful army base, this abandoned military fort on the coast of Monterey Bay has been left to the elements.

At this California chicken ranch, four bucks will get you 18 eggs and a chorus of dancing animatronic poultry.

An ominous concrete cube cuts a dystopian silhouette atop this California mountain.