Seems that I have been selected to receive a Random Act of Smileness!
The Bingham Canyon Mine is an open-pit mining operation extracting a large porphyry copper deposit southwest of Salt Lake City, Utah, USA, in the Oquirrh Mountains. It is the deepest open-pit mine in the world.
The mine has been in production since 1906, and has resulted in the creation of a pit over 1.2 km deep, 4 km wide, and covering 7.7 km². According to Kennecott, it is the world's largest man-made excavation. It was designated a National Historic Landmark in 1966 under the name Bingham Canyon Open Pit Copper Mine. (source)
Thank you so much Tina (mmtnsage)!