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

This cave was hidden for thousands of years, storing the worldly goods of ancient Native Americans.

These abandoned grain silos and tunnels are an urban exploration dream.

Inside this striking glass building, visitors can see thousands of dinosaur fossils in the positions that nature deposited them more than 150 million years ago.

This prehistoric sinkhole lured exclusively male mammoths to their death, much to the delight of science.

A little-known hot spring haven right below the highway.

Rushing water plunges over a 100-foot drop created by an ancient lava flow at this majestic waterfall.

This lake in the Cascades lives up to its name, disappearing down a hole every spring.

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

Hollowed out cedar log tubs set in an ancient towering forest.

This frequently-photographed waterfall takes only a short hike to visit.

Seemingly grown on some other world, these New Mexico rock formations look like a disused science fiction set.

An enormous park-like oasis, full of famous Chicagoans' graves.

Private collection of art inspired by cabinets of curiosity.

A reproduction of earth's many biomes.

A shop full of natural curiosities, carnivorous plants, and costumed taxidermied mice.

A lush green oasis in the middle of Chicago.

Carnivorous plants, medieval aphrodisiacs, and the largest original wood structure glass conservatory in the western hemisphere.

Stroll through a wonderland of stupendous moss-covered trees.

One man has carved a number of natural New Mexico caves into psychedelic sandstone temples.

Crystal clear lake with a shoreline of travertine located in a Colorado canyon.

High on a hill overlooking Los Angeles lives a world famous, high power conical Tesla Coil.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.