An abandoned stretch of highway, deteriorating next to the operational one.

The superstar of Cold War nuclear bunkers has been featured in countless films but is now barely operational.

When ecosystems collide in the arid Southwest.

Less a museum than a bizarre fantasy world created by artists and engineers.

The Boston square dedicated to the dark poet who was born nearby.

The highest bridge in America was built for an almost unnervingly small amount of money.

This quirky curiosity shop takes its cues from the world's bazaars.

A monument to the art of slicing people open.

An acoustic anomaly with a mysterious cause.

These eerie outliers of the lightning bug family glow a mysterious blue color.

Strange red rock formations that have been attributed to a higher power for hundreds of years.

All that's left of the quintessential "cabin in the woods."

The angel of death appears to weep black tears at this grave marker.

The world's longest known cave system.

The "Seinfeld" diner.

Possibly the most beautiful carillon in the world, set atop Iron Mountain in Florida.

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

A breathtaking array of ancient Pueblo structures and artifacts counterintuitively preserved by neglect.

The first declared National Monument in the United States.

Home to items never before seen by the public.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

Mysterious rocks that ring musically when struck.

This shop for all your super spy needs hides an educational secret.