Last September, I went on a 30 mile long mountain-biking trip on the Montana/Idaho border. It’s an old rail-road grade that has been turned into a mountain biking trail. There is ten tunnels, and 7 really high trestles. My favorite tunnel (and the longest one) crossed the border from Montana to Idaho, and was 1.6 miles long. I took this picture from one of the trestles. Across the valley is another one of them!