Bingham Pit, Utah

"It is 2.5 miles wide and 3/4 mile deep. Looking into it is like looking into space," the Center for Land Use Interpretation suggests. It's Utah's Bingham Canyon Copper Mine, and it just might be "the biggest hole on earth."

[Image 1: CLUI; Image 2: here; Image 3: here].

Also, see Placement's One Hundred Years Towards Hell; as well as BLDGBLOG's World's largest diamond mine.