There's an open pit diamond mine called the Mirny Mine in East Siberia, Russia. It's very deep. At over 1,700 ft deep, it's the 4th deepest mine in the world. It also has a diameter of over 3,900ft. This makes it the second largest excavated hole in the world!
The mine is so large, that the airspace above it was closed for helicopters. Due to the size of the mine, the air currents above it become really dangerous. There were a few reported cases of helicopters crashing after being sucked into the mine due to the pressures from this air flow!