Kimberley Big Hole - South Africa: Apparently the largest ever hand-dug excavation in the world, this 1097 meter deep mine yielded over 3 tons of diamonds before being closed in 1914.
Glory Hole - Monticello Dam, California: This is the 'Glory Hole' at Monticello dam, and it's the largest in the world of this type of spillway, its size enabling it to consume 14,400 cubic feet of water every second (note: a glory hole is used when a dam is at full capacity and water needs to be drained from the reservoir).
Bingham Canyon Mine, Utah: This is supposedly the largest man-made excavation on earth. Extraction began in 1863 and still continues today, the pit increasing in size constantly. In its current state the hole is 0.75 miles deep and 2.5 miles wide and covering 1,900 acres.
Great Blue Hole, Belize: This incredible geographical phenomenon known as a blue hole is situated 60 miles off the mainland of Belize. There are numerous blue holes around the world, but none as stunning as this one.
Mirny Diamond Mine, Serbia: I'm pretty sure most people have seen this one. It's an absolute beast and holds the title of largest open diamond mines in the world. At 525 meters deep, with a top diameter of 1200 meters, there's even a no-fly zone above the hole due to a few helicopters having been sucked in.
Diavik Mine, Canada: The mine is so huge and the area so remote that it has its own airport with a runway large enough to accommodate a Boeing 737. It looks equally cool when the surrounding water is frozen.
Sinkhole in Guatemala: These photos are of a sinkhole that occurred in Guatemala. The hole swallowed a dozen homes and killed at least three people.
The most terrifying hole of all: This is the famous 'Rat Hole' that you've read so much about lately. It is capable of swallowing trillions upon trillions of U.S. dollars from the real economy each and every year.
Hat tip: Dave W. Linked by: Ace of Spades. Thanks!