This diamond mine in eastern Siberia (Mirny, to be exact) is so deep that the surrounding “air zone… is closed for helicopters” after “a few accidents when they were ‘sucked in’ by downward air flow…” More stuff about it here.
This diamond mine in eastern Siberia (Mirny, to be exact) is so deep that the surrounding “air zone… is closed for helicopters” after “a few accidents when they were ‘sucked in’ by downward air flow…” More stuff about it here.