Take a drunken tour inside the world's largest known geode.

In Rickwood Caverns, visitors can travel hundreds of feet underground and see beautiful formations unique to the region.

Since it formed millions of years ago, this cave system has been a sacred burial ground, a Prohibition-era speakeasy, and the center of an amusement park.

The only Florida state park with publicly accessible caves.

A humid oasis combines recreation with exploration in a unique underwater cavern.

The biggest cave system in the Arabian Peninsula is home to a rare variety of blind fish.

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

A cave's rare beauty held a cavernous secret hidden underground.

A waterfall 600 ft. inside a mountain, once the bane of gold miners, is now a spectacle of nature.

This ancient cave is home to a museum, bar, and is filled with fluorescent minerals.

This central Nevada cave is the spiritual home of ancient and enigmatic pictographs.

A gothic palace of endless stalagmites and pseudoscorpions waits within one of the world's most beautiful caves.

Each winter this underground cave forms a dazzling ice palace.

Sail through this subterranean show cave that is home to a legend that would go on to name nearly everything around it.

Historical figures from New York City's Catholic community reside in Midtown.

The beautiful tunnel that ran from the lobby to Penn Station is still hidden underneath 34th Street.

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

There's a piece of New York City transportation history hidden in plain sight at a Manhattan subway stop.

It's 2 billion years old!

Underneath downtown Lincoln resides a network of caves that was also the city's first brewery.

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

This Old West prison built into the side of a cliff was said to be inescapable.

An off-the-beaten path cave with an underground lake.

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