A half-mile long and three stories high, this bridge over the Des Moines River Valley mimics a descent into a mine shaft.

"Looks so real, it's scary!"

A glimpse into the sacrifices of military members during World War II.

The debris forms a solemn memorial to those who died in a 1963 accident.

The “Grand Canyon of Maine” is a three-mile gorge full of striking geological features.

A gothic palace of endless stalagmites and pseudoscorpions waits within one of the world's most beautiful caves.

This rest area is also home to a remarkable petroglyph site.

This central Nevada cave is the spiritual home of ancient and enigmatic pictographs.

This little-used trail winds through the highest mountain range in central Nevada with sections around 10,000 feet.

The "world's smallest volcano" has been used to store meals and dispose of dead bodies.

These ominous lava formations were said to be an entrance to the netherworld so of course they inspired a famous metal band.

A sulfuric martian landscape that looks far better than it smells.

A spectrum of colors awaits visitors to one of Mexico's most gorgeous bodies of water.

Squeezing inside this deep, narrow canyon reveals a festival of desert colors.

Known as the "Valley of the Moon," this Jordanian wadi is one of the most amazing desertscapes on Earth.

These otherworldly formations were shaped over millions of years by the forces of nature.

In Northeastern Iceland lies something of an oxymoron: a steaming desert.

These gleaming gypsum sand dunes are the second-largest in North America.

A former travertine mine traces the geological history of this unique desert filled with crystalline blue pools.

In a strange timezone anomaly, Daylight Saving Time here sets the clocks forward just 30 minutes.

This dramatic sea spire is home to the world's rarest insect and is part of the lost continent of Zealandia.

Climb right into the heart of this colorful Iceland volcano.

A winding, blood-red tunnel of hardened lava navigable by foot.

Colorado's only active volcano last erupted around 4,000 years ago.