Limestone caves with spectacular showcase chambers.

The bullet-riddled wall from the St. Valentine's Day Massacre, bloodstains enhanced for your viewing pleasure.

This sacred cavern, 400 feet deep, is home to millions of bats and an ancient burial ground.

Where monkeys run wild and the humans are caged.

Once a menacing challenge for trailblazers, this trail is now the most scenic drive in Utah.

These banned cigarette vending machines now sell little pieces of pocket-sized art.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

Paris' fabled purveyor of exotic taxidermy and natural history curios.

The history and future of cannabis.

The story of Two Guns, Arizona could easily be described as a Shakespearian tragedy on Route 66.

The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

The L.A. Zoo has a secret garden of rare bootleg cycads, a palm specimen dating back 280 million years.

This hidden green space is the city's second largest conservatory.

An abandoned quicksilver mining town surrounded by the Big Bend parks.

Only known mainland rookery of the threatened Stellar sea lion.

The drama of nature in full effect in this Nevada State Park.

Scattered throughout London are ancient remnants of the city's former bounding wall.

Moonbows over Kentucky.

A Prada store in the West Texas desert that is never open for business.

Mysteriously stacked storefront paths give this medieval British town an iconic style like none other.

An oddities shop that dabbles in the deathly and beautiful.

San Diego's most historic and haunted home.

Standing in a state of "arrested decay," this ghost town allows for a detailed peek into Gold Rush life in an unusually harsh climate.

A tribute to Ponce de Leon's supposed quest for eternal youth.