Alaska Central Railroad: Tunnel No. 1 - Credit: Wikimedia Commons
Alaska Central Railroad Tunnel No. 1, also known as the Loop District Tunnel No. 1 is a historic railroad tunnel located about north of Seward, Alaska, in the Placer River Valley, Kenai Peninsula. The tunnel was dug in 1906 and served the Alaska Central Railroad and later the Alaska Railroad until the route in the area, known as the "Loop District" was rerouted in 1951. Read more on Wikipedia
Source: en.wikipedia.org