Secret North Korean passage discovered below the world's most dangerous border.

The site of many tense prisoner exchanges across the Military Demarcation Line between North and South Korea.

The fifth-longest natural arch in the world, and the longest outside China.

Thousands of pieces of art have been carved into the rock at the site of an ancient volcanic eruption.

The official atomic museum of the United States explores the explosive and productive history of a much maligned energy source.

When ecosystems collide in the arid Southwest.

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

This nearly abandoned town was once a thriving mining community until a series of fires.

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

The largest source of fossilized insects anywhere.

Thanks to a quirk of elevation this gift shop produces magic doughnuts that are found nowhere else on Earth.

The honor of highest point in Michigan was almost given to the wrong peak before this mountain won out by 11 inches.

"The Most Boring Road in the State."

Large one-man sculpture park in Michigan.

This lone tree and dramatic sandstone outcropping are so beloved by Michiganders they can be found on one of the state’s coins.

The world's tallest doric column is this Ohio monument to a naval victory in the War of 1812.

A favorite of Amelia Earhart, ranking among those rare bridges that can be crossed without changing sides of the river.

The highest point in Indiana is curated by an Eagle scout but may be in danger of losing its record to a nearby garbage pile.

In this relatively flat state the highest point is an honored place.

The former broadcast site has been reimagined as a museum about the medium.

Inside houses a vast collection of military aircraft and missiles spanning the ages.

The world's longest known cave system.

The highest point in Florida is still the lowest high point in the country.

Designed by Maya Lin, the memorial honors 41 individuals who died fighting for equal rights between 1954 and 1968.