The Largest Open Pit Diamond Mine in the World

Mir Mine, also called Mirny Mine, is the second largest excavated hole in the world. It is 525 meters (1,722 ft) deep and 1,200 meters (3,900 ft) wide. The hole is so big that even the airspace above the mine was closed to helicopters as there were several incidents of them being sucked in by the downward air flow.
The mine was discovered on June 13,

1955 by Soviet geologists Yuri Khabardin, Ekaterina Elagina and Viktor Avdeenko. They found traces of volcanic rock kimberlite which are usually associated with diamonds. This finding was the first success in the search for kimberlite in Russia, after numerous failed expeditions of the 1940s and 1950s. For this discovery, in 1957 Khabardin was given the Lenin Prize, which was one of the highest awards in the Soviet Union.

The development of the mine had started in 1957 in extremely harsh climate conditions. Seven months of winter per year froze the ground into permafrost, which was hard in winter, but turned into sludge in summer. Buildings had to be raised on piles, so that they would not sink in summer, and the main processing plant had to be built on a better ground found 20 km away from the mine.

The winter temperatures were so low that car tires and steel would shatter and oil would freeze. During the winter, the workers used jet engines to defreeze and dig out the permafrost or blasted it with dynamite to get access to the underlying kimberlite. The entire mine had to be covered at night to prevent the machinery from freezing.