The Mir diamond mine in Siberia is the deepest ‘proper’ man-made hole. It’s 525m deep and 1,200m across. There’s a no-fly zone above it because the downdraft created by the hole had caused several helicopters to crash.
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"Silence is an ocean. Speech is a river." Therefore chose to swim in the ocean Hectors Dolphins, Kaikoura, South Island, New Zeal...
