Keystone, SD Today was an explore day. Like all good tourists, we drove the Needles Highway. 14 miles long and finished in 1922, the highway is named after the high granite "needles" it winds among. We drove to Sylvan Lake, a lovely spot. The lake was featured in Disney's 2007 film National Treasure: Book of Secrets. We then spent some time in Custer State Park. The park is home to a herd of 1500 free roaming bison. We did not find all 1500 but we did find a substantial number – some of them causing a traffic jam as they seem to think they have as much or more right to be on the road than we do! Our return to Keystone was via Iron Mountain Road. The highway passes through three tunnels blasted through sheer granite walls. Owing to the narrow roadway, sharp u-turns and pigtail turns, maximum speed limits of 25 mph dropping to 10, and low tunnels, the road has very little traffic. The vehicles that do travel this road are almost exclusively sightseers, majorly because the tunnels frame a view of the Presidents on Mount Rushmore. We were happy to do our part.