Excavation in the Russian Mirny Diamond Mine began in 1995. On the day of its closure, it was 525 meters deep and 3900 feet wide. Such a size made it the second largest man made hole in the entire world. Joseph Stalin, then leader of the Soviet Union, ordered the construction of this mine to produce diamonds. During its most productive years, the mine produced about 10 million carats of diamonds annually. No one ever really knew how it was able to do so well. The mine was permanently closed in 2004. The most disturbing fact about this place is that, after its closure, it began to cause severe problems for passing air crafts, such as sudden currents and unexplained air temperature differences. Because of this, the air space above the mine is permanently closed. Whatever happened down there certainly has an effect on planes, which is something that most would find quite disturbing.