Bioluminescence in the reefs of the Maldives causes the sea to glow like a starry night sky.

An underwater restaurant, surrounded by a coral reef.

Monkeys inhabit the lush forest surrounding ancient Mayan ruins once considered sacred.

An important Mayan religious and trading center dating back to 200 BC.

At least seven hues of blue and turquoise make this freshwater lagoon unique.

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

Discovered by cows, these upstate New York show caves are presented with a healthy dose of psychedelic folk art.

This Irish show cave is said to have been the site of a Viking massacre that claimed 1,000 lives.

Hidden in Central Park's Ramble is a troublesome cave buried just beneath the surface.

Holy Hindu shrine in an enormous, monkey-filled limestone cavern.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

River pirates, murderous bandits, and serial killers used this Illinois cave as their debauched hideout.

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

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

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

"Iron Age" creatures fill this huckster's rusted metal sculpture garden.

This impressive former palace contains a hidden gem for fans of modern sculpture.

The enormous appendage offers spectacular views of Colombia's Huila Department.

A sculpture park that takes the use of clay to a whole new level.

An outdoor sculpture park of giant pink robots and post-apocalyptic Christmas scenes.

It took an artist 20 years to create this sprawling sculpture garden honoring the area's ancient inhabitants.

A former palace that showcases weapons, jewelry, clothing, furniture, musical instruments, and more from the Peshwa Era.

A hamlet full of permanent Christmas spirit holds one of the earliest theme parks in the United States.

Secluded amid upstate New York’s Adirondack Mountains lies this subterranean emblem of a nation on the brink of nuclear war. And it's for sale.