A medieval castle in the middle of rural Texas.

A popular swimming hole that hides one of America's most deadly diving spots.

A modernist landscape of water and sci-fi concrete.

A natural sandstone bridge hidden in the Sewanee forest.

This tiny 19th-century tunnel was built so a man could move his cows from one field to another.

This defunct, fortress-like prison has been the setting for several movies.

This former maximum-security prison is creepy, sobering, and supposedly haunted.

Labor provided by Great Depression-era programs restored these 25,000 acres in Tennessee.

This funicular railway rumbles along for a mile up the nearly vertical face of Chattanooga’s Lookout Mountain.

Mile-long cave system near Great Smoky Mountains.

Better known as the "Body Farm," this unique research facility has been studying how human bodies break down since the 1980s.

Visit this playground of waterfalls, caves and sinkholes.

For two weeks every June, fireflies in the Smoky Mountains perform an astonishing light show.

This former mining railroad is one of the best-preserved short lines in North America.

How a bat poo mine became a major Native American archaeological site—and connections to legendary red-haired giants.

An unusual waterfall in the Santa Rosa Range, within the Great Basin of Nevada.

In the little-known Pine Forest Range in northwestern Nevada, a natural lake of glacial origin.

An unusual slot canyon in the Aztec/Navajo Sandstone has a cross-section like an inverted old-fashioned keyhole.

An old railroad grade built for the construction of Hoover Dam is now a recreational trail featuring several tunnels and sweeping views of Lake Mead.

A hidden slot canyon in the southern Nevada desert makes an unexpected oasis and scenic hike.

A breathtaking 19th-century trail overlooks Lake Tahoe.

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

This Nevada lake holds its titular natural pyramid and, if the legends are true, a number of dangerous spirits.

The drama of nature in full effect in this Nevada State Park.