Two massive and unstable sinkholes are yearning to unite, and their consummation could be catastrophic.

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

Wondrous sandstone hoodoos where Native Americans collected clay for pottery, 9,000 years ago.

Dramatic river bend surrounds a natural red-rocked pedestal.

An emerald-green grotto just a short trip from Austin.

Rippling sand dunes frozen in the Arizona rock.

Giant busts of 42 U.S. presidents are sitting in a field in Virginia.

One man's lifelong collection of 10,000 rare steins tells the story of beer drinking from 1350 to today.

A sign marks the plane crash that caused two nuclear bombs to fall in North Carolina.

A six-foot pair of socks hangs from a drawer of the world's largest bureau.

The U.S. Supreme Court's secret Cold War relocation facility in the mountains of North Carolina.

A young state senator's deathbed plea to be buried inside a rock resulted in this unusual grave site.

When you can afford only half a road, you build only half a road.

Bubbling up from deep underground is the warm crystal clear water that fills the Warm Springs Pools, America's oldest spa.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

Yes, this monument is aware that it is about 20 miles away from the actual center of the United States.

This water tower slanted at an uncomfortable angle off the old Route 66 was an ingenious marketing ploy.

The man who wasn't there.

This razorback ridgeline has doubled as a scenic drive since the early 1900s.

Kentucky, Tennessee, and Virginia meet at this point in the Cumberland Gap.

This multi-story wooden waterpark offers homemade thrills.

Eight feet in diameter and more than 24 feet around.

Tiny observatory made big contributions to the study of the Earth's motion.

The Cadillac Ranch for monster truck aficionados.