Siberia claims to have the biggest man-made hole, in the world. It’s a diamond mine near the town of Mirna.
The Kennecott Copper pit in Utah (outside of Salt Lake City) is the world largest and monetarily richest quarry. More information and pictures of it.
Now arm-chair pundits get to fight it out over which one truly is the biggest man-made excavation. I’d vote, but I’m biased towards this pit I dug back in elementary school… it was known to swallow plastic action-figures whole.