So I was reading about the biggest hole in Russia
The gaint hole is actually a diamond mine in Eastern Siberia near the town Mirna. It is 525 meters deep and 1.25 km in the diameter.
The suction above the hole resulted in several helicopter crashes, so all flight above the hole is prohibited now.
and learned about Bingham Canyon Copper mine via the post comments. The facts about the mine are fascinating. And the pictures are impressive. I wonder if this is what the West Virginia mountains will look like in 100 years. (see also)