This spooky tunnel is the longest in North Dakota at 1,458 feet long. It was built between 1912 and 1913 mostly by hand with the help of horses and mules pulling machinery. Both the bridge and tunnel were built by the Great Northern Railroad and were to be a part of the unfinished Montana Eastern Railway. Today, it is only open to pedestrians or cyclists. Parking is available at Sundheim Park on the west bank of the Yellowstone River. To get there take State Route 200 and at the park's access road, then head south. The bridge and tunnel are open 24/7.