This 17-mile stretch of U.S. Route 16A showcases the mountain curves of the Black Hills as you make the trip from Mount Rushmore to Custer State Park, one of the Midwest's most underrated parks.

The curves often seem to undulate like two ribbons, but the animation can also seem to have depth, with one curve seeming to be further back than the other. The dotted arcs can also look like a ...