Located in Custer State Park, Needle's Eye is a narrow one-lane tunnel on South Dakota Highway 87 (also known as Needles Highway). As part of the Peter Norbeck Scenic Byway, this highway stretches miles through spectacular mountains with crazy granite formations and Black Hills spruce forests. The Needles Eye Tunnel is truly unique in that it's a small opening blasted through sheer granite walls. Be mindful of the size restriction to avoid getting stuck in the tunnel.