Five ancient libraries, little changed for centuries, preserve a medieval archive of Quranic lore and civic documents

An abandoned NSA listening post on Berlin's "Devil's Mountain."

Surreal riveted sea forts once protected the Kent shores from German attack.

A part of the world's largest marsh seems to be growing bright red Martian grass.

The remnants of an early American attempt at missile defense.

These conical kilns measure an impressive 30 feet in diameter, and were once used to produce charcoal for a local blast furnace.

The world's largest wooden trestle stretches across this desert canyon in Anza-Borrego Desert State Park.

During WWII the U.S. Navy conducted primitive drone strikes on this Lake Michigan lighthouse.

Joe Minter is only doing the work of God in his yard, he says.

An internationally-recognized dark sky sanctuary lies in northern Nevada, near the Oregon line.

These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

An abandoned lighthouse awaits its destiny: being buried under shifting sand.

A skeletal collection of former nautical mainstays.

This ancient settlement contains some of the largest earthen mounds in North America.

The second-largest ceremonial mound in the United States is an artificial hill that is loosely shaped like a pentagon.

The highest point in Louisiana, Driskill Mountain at 535 feet above sea level.

These abandoned waterworks are crumbling into the Potomac River.

A derelict bit of transportation infrastructure hidden in the woods.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

100 years later, they're still down there.

The crumbling ruins of this southern American fort have survived storms, war, and cults.

This whimsical stacked cabin looks like something out of a children's book.

Artistic cabins actually grow deep in the Canadian wilderness.

Four-story concrete hotel never opened to customers.