The ominously named cave is home to some remarkable ancient art.

More than five miles of underground passageways.

A spring-fed pool so deep it's used for scuba diving as well as swimming.

The summer home of the largest colony of bats in the world.

A 90-year-old underground water reservoir offers a more industrial kind of tranquility.

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

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

An enormous pink granite batholith, long attributed with spiritual powers by the Tonkawa Indians.

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

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

A popular swimming hole that hides one of America's most deadly diving spots.

A modernist landscape of water and sci-fi concrete.

Take an otherworldly journey in a school dedicated to out-of-body experiences.

A clear blue swimming hole with hidden caves, still unexplored.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

One of Canada's most incredible rare book collections holds hundreds of thousands of gorgeous tomes that the general public can touch.

Birds with backpacks expedite film development for a rafting company on a remote Colorado river.

Each year, teams of the world's best snow sculptors have 65 hours to create frozen masterpieces.

A research lab and hands-on museum where visitors can experiment with retro technology.

There are eight natural springs around town, each with a slightly different taste.

This 19th century jail was mainly used to incarcerate the drunk and disorderly.

One of few remaining antique carousels with stationary animals in the U.S.

16,500-acre ranch filled with American heritage, geological wonders, and a giant pile of tires is the crown jewel of an intriguing tug-of-war.

The world's largest carnivore sanctuary is home to over 450 meat-eating rescues.