Mirrny Diamond Mine
This mine is more than 1,700 feet deep and 3,900 feet wide, which makes it one of the largest excavated holes in the world. Open-pit mining was stopped in 2001 but underground mining has been active since 2009. Following the collapse of the Soviet Union in 1991, Sakha diamond company reported that annual profits from the mine exceeded $600 million. With so much money at stake, security will be very tight.