Mysterious craters may have been home to an ancient cult.

A Texas-sized particle collider that was abandoned due to its Texas-sized budget.

Genesis of modern hydroelectric power.

Collection of antique science instruments displayed in recreated 1870-1930 laboratories.

A roaring, awe-inspiring double cascade of icy water flows through woodland Oregon like something out of a Tolkien novel.

A library built during San Francisco's pioneer times is a student's retreat, bibliophile's sanctuary, and chess player's delight.

This WWII-era military installation once held an entire city within its walls - now, its walls are falling down.

A former French military respite turned jungle tourism hotspot.

The deepest lake in the United States, and once the site of epic destruction that lives on in legends.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

One of many reminders of Tesla's scientific contributions overlooks the falls which inspired him.

A stunning, abandoned limestone quarry in southern Indiana provided the stone to erect the Empire State Building.

Constantly maintained, this organ is playing a six-century long composition by John Cage.

Yugoslavia's biggest underground airport lies in ruins.

A military museum and library dedicated to the citizen soldier.

This three-chambered cave is the only protected natural bat hibernaculum in Quebec.

DIY collection of eclectic holdings.

Turning night into day in Victorian-era Austin to thwart a serial killer.

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

Slaughterhouse Five opens its dank doors to fans of Kurt Vonnegut.

A mysterious air force base built to resemble a Long Island fishing village.