This Polish cave has housed a dragon, a brothel, and an enduring legend.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

Through the colossal entrance to this cave you'll find limestone tubs and an underground waterfall.

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

At the right time of day, sunlight floods through the roof of this cave and illuminates the small pavilion hidden within.

An ancient cave system in Tennessee’s Appalachian foothills converted to a 1,200-person music venue.

This curious fresh and salt water lake holds a secret that draws in deep divers from around the world.

Made famous by 'Star Wars,' these troglodyte homes face an uncertain future.

Few things look more out of place than the electric blue ponds in the reddish-brown desert of Utah.

A crack flared at the base provides a pathway completely through a sandstone ridge near Moab.

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.

Though difficult to access, this stunning cave has a place in Scotland's poetic history.

It's believed a local adventurer spent 50 years living inside this cave.

This cave was once thought to be a hiding place for the devil.

This narrow path was cut right into a French mountainside to feed the country's early naval expansion.

The true depths of these stunning Moroccan caves are unknown.

Houses are tucked between, on, and underneath giant boulders.

This site is both a remarkable reminder of the town's mining history and a fantastic government blooper.

Journey through various trails to discover a land before time along the Chazy Fossil Reef.

A massive cave complex boasts some of the clearest water (and most charming bats) in the world.

One of the world's largest salt caves is filled with fragile salt sculptures, salt rivers, and huge salt megadomes.

This cave located in the badlands of Somaliland contains some of the oldest cave art in Africa.

The largest known open fault in the United States is basically a giant natural refrigerator.

Europe's second largest ossuary wasn't discovered until 2001.