2. Mirny Diamond Mine, Russia
This Siberian open-pit mine was began in the Stalin era to furnish industrial diamonds to the Soviet Union. Digging started in 1955, creating the second largest man-made hole in the world. It is observable from space and ’s almost a mile wide. Gossip has it, aircraft are forbidden from flying over the abyss for anxiety of the air currents sucking them down. Digging through Siberian permafrost has its challenges, so the mine closed in the 2000s.