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
Glory Hole - Monticello Dam, California
A glory hole is used when a dam is at full capacity and water needs to be drained from the reservoir. It is the largest spillway of this type in the world. It consumes 14,400 cubic feet of water every second.