At the Eagle Butte Coal Mine, 5 mi north of Gillette, shovels and haul trucks dwarf anything you're likely to see in a science-fiction movie. There's a surprising amount of wildlife, from falcons to deer to bobcats, dwelling in and around the huge pits. You can register for the summer tours of the mine at the Gillette Visitors Center.
Gillette Visitors Center, Flying J Travel Plaza, 1810 S. Douglas Hwy. 59, Gillette, Wyoming, 82716, USA