A mile-long pit holding 900 feet of acid water full of metal
A former open-pit copper mine at Butte, a mile long and half a mile wide, going down about 1,780 feet. Roughly 900 feet of that is now water, and the water is the point: it sits at pH 4.1 to 4.5, about as acid as beer or tomatoes, and it is loaded with heavy metals leaching naturally out of the exposed rock. Butte dug the richest hill on earth and this is what was left when the digging stopped. Look at it, understand what it is, and do not go down to the water.
Other places on the map within a couple of hours of here.
