A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

Home of a 28-foot tall stalagmite known as the War Club.

Water of undetermined depth has attracted rare fish and cult leaders alike.

These Great Lakes sea caves accessible by boat in the summer turn into temples of ice reachable by foot in the winter.

Don't blink or you'll miss it.

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

A popular tourist cave with a dark past.

The only Florida state park with publicly accessible caves.

Limestone caves with spectacular showcase chambers.

Bizarre Cavern.

In a 345-million-year-old cave that's 200 feet underground, dinner awaits.

Wild lights and sound effects turn a walk through some caves into an eye-popping 1960s tourist attraction.

One of the largest, oldest, darkest, quietest motel rooms in the world.

More than five miles of underground passageways.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

The longest navigable underground river in the United States is home to countless blind and albino animals.

400 million-year old limestone caverns nestled in the Ozarks served as shelter and a hideout for cultures throughout North American history.

These tourist trap caverns are said to be the former home of a legendary Pennsylvania Hermit.

European castle ruins in an American state park are actually the product of death and grief.

If there's another drive-through golf-cart bar in a bat-filled cave on top of a mountain, we don't know about it.

An unexpected but incredible collection of wildlife dioramas spanning rainforests, swamps, forests, and plains.

The show pony of cave systems, Fantastic Caverns manages to live up to its name.

A swimming hole in the historic industrial quarry that supplied the marble for the Baltimore Washington Monument.

The remains of an old sawmill, gristmill and the surrounding industry dating back to the 18th century.