The Kennecott Copper Mine was kind of on our to-see list, so when a free admission coupon popped up, we took advantage. It's about 1/2 hour to drive all the way to the east side of the valley. We went with my cousins Jill and Sarah. The very impressive mine uses 80 trucks the size of a house to carry loads filled using electric shovels that can lift the equivalent of 50 cars. Another really interesting fact we learned is that the material being mined is only 1% copper! Somehow they've managed to make that profitable.
This place is pretty far out of the way, and doesn't have much to entertain young kids. Mine were pretty restless. It was interesting though. Admission is regularly $5, and all proceeds go to charity.
I wasn't kidding about the trucks being the size of a house.