The second-largest man-made hole in the world (surpassed only by the Bingham Copper Mine in Utah) is a diamond mine located on the outskirts of Mirny, a small town in eastern Siberia. Begun in 1955, the pit is now 1,722 feet deep and 0.78 miles in diameter. Stalin initially ordered construction of the mine to satisfy the Soviet Union's need for industrial-grade diamonds.

The harsh, frozen Siberian landscape made working on the mine a difficult proposition at best. Jet engines were turned on the unyielding permafrost in order to melt it; when that failed, explosives were used. During its peak years of operation, the Mirny mine produced over 10 million carats of diamonds annually, a good percentage of which were gem-quality.

Operations ceased in 2001, but the site didn’t lie dormant for long. Diamond mining now takes place in great volumes at the Mir Underground Mine, which lies just underneath the original open pit. To get to the base of the pit, massive 20-foot tall rock-hauling trucks travel along a road that spirals down from the lip of the hole to its basin. The round-trip travel time is two hours.

More on the Mirny Diamond Mine can be found on Atlas Obscura.

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