Its dark depths conceal millions of rare, delicate crystal formations.

This quirky roadside attraction dives into the many theories surrounding North America's most infamous hairy cryptid.

An expansive and intricately restored mansion remains from over a century ago--and so do its ghosts.

Massive prehistoric mammals used these stones as oversized scratching posts.

This museum looks at the history of one of America's most famous prisons and most beloved albums.

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

A life-sized mammoth sculpture marks the spot where the remains of a Columbian mammoth were discovered in 2005.

A fleet of automotive automatons sleep in this otherwise unremarkable urban garage.

This small monument to the great inventor contains a time capsule and a Wi-Fi hotspot.

Guarded by the Angel of Grief, the Stanford family tomb attracts an odd mix of halloween revelry and somber contemplation.

A humble garage, world-famous for being the epicenter of a technology revolution.

The graffiti-covered remnants of a former triangulation station are balanced precariously on this California peak.

San Francisco Bay's ghost town.

A trail weaves through the verses of a poem illustrated by stone sculptures inspired by Native American pictographs.

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

Neither Spanish settlers nor anyone since has been able to tell who built these strange California rock walls.

A vast city of the dead, where the deceased outnumber the living by more than a million.

The peaceful gravesite of a rugged wild west gunman echoes the touching story of his last days.

Once the largest windmill outside of Holland, with enormous 114 foot sails.

This historic California cemetery holds the bodies of veterans of both the Civil War and the Donner Party.

The one-time watch house for incoming ships at the Golden Gate now stands abandoned and hidden in trees.

Big gun installations, built over a massive cemetery, now abandoned & hidden in trees.

An artsy hidden staircase leads to breathtaking views of San Francisco.

The remains of a 12th-century chapter house in Golden Gate Park.