At 705 feet high, Brazil's "House of Stone" is the largest cave mouth in the world.

This wonderful rock formation constitutes the first geopark in Uruguay.

Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

A three-tiered waterfall plummets from a mountain cave with amazing views over the countryside.

Enchanting cave with a river crashing through the roof.

A jungle cave in Peru of unknown depths, otherworldly sounds, and strange nocturnal birds that navigate by echolocation.

A flooded Mexican cave that hides a river beneath the water.

These azure waters were thought to lead to the Mayan Underworld.

If you can look past the nearby sewer pipes, this urban sinkhole grotto is a mini-paradise.

This popular cave pool is truly magical, despite the crowds.

Take a dip beneath the stalactites in this amazing cenote.

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

Enormous lake at the bottom of a unique cave system.

The perfectly named cave drop is the deepest in the continental United States, almost matching the height of Seattle’s Space Needle.

The world's longest known cave system.

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

This large midwestern cavern features impressive rock formations and an underground waterfall.

Gorgeous cave resemble a winter wonderland.

In the northernmost city in the world, it's illegal to be buried because it’s too cold for bodies to decompose.

The world's northernmost flowers cling tenuously to life on desolate Kaffeklubben Island.

Earth's greatest purely vertical drop at 4,101 feet.

An experimental forest at the foreground of arboreal science is also the canary in the coal mine for climate change.

This isolated structure beckons adventurers with sublime views of the Faroe Islands.

This isolated and westernmost point of the Faroe Islands archipelago is home to thousands of seabirds.