Drift through underground caves on a tube.

The short hike is worth the stunning views and crystal blue waters of a secluded beach.

Puerto Rico's oldest rum producer started its 140-year-old business with "a little barrel."

This former sugarcane transport tunnel is now a portal to a lovely beach.

This bleach-white graveyard overlooking the ocean is accessed through a tunnel.

An enchanting natural wonder in Puerto Rico's Camuy River Park.

The bat-covered home of one of the world's most popular brands of rum is located on a tropical Art Deco campus.

The world's brightest bioluminescent bay.

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

One of the oldest producers of hand-folded fortune cookies still uses its original secret recipe.

A Barbary Coast watering hole built into a Gold Rush shipwreck.

Gold Rush-era tombstones line the park's paths.

The tea room that pushed the boundaries of adorable straight into...we can't find the words.

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

The eerie ruins of an isolated abandoned town nicknamed "the Widowmaker" for its deadly gold mine.

There's nothing creepier than a cemetery next to a clown motel.

This set of three large, volcanic hot springs is a favorite haunt for intrepid divers.

A cemetery full of touching tombstones from a community of railroad workers, uranium miners, and Cold War missile launchers.

For over a century, it has been a tradition to raise a flag at the top of this 450-foot sandstone pillar on the 4th of July.

The tallest bridge in California was constructed for a project that was eventually cancelled.

The now-abandoned tunnels were built for the transcontinental railroad on the route where the first wagon train entered California.

Bits and pieces from the ill-fated Donner Party's winter cabins.

The only surviving prototype of Buckminster Fuller's revolutionary car.

An eccentric millionaire's personal curio collection includes at least one shrunken head.