The Simplon Tunnel is a railway tunnel on the homonymous line that connects Brig, Switzerland and Domodossola, Italy, through the Alps, providing a shortcut under the Simplon Pass route. It is straight except for short curves at either end. It actually consists of two single-track tunnels built nearly 15 years apart. The first to be opened is 19,803 m long; the second is 19,824 m long, making it the longest railway tunnel in the world for most of the twentieth century, from 1906 until 1982, until the Daishimizu Tunnel opened 76 years later.
Culminating at a height of only 705 m above sea level, the Simplon Tunnel was also the lowest direct Alpine crossing for 110 years, until the opening of the Gotthard Base Tunnel in 2016. The tunnel has a maximum rock overlay of approximately 2,150 m, also a world record at the time.
Wikipedia https://en.wikipedia.org/wiki/Simplon_Tunnel
Address 28868, Italy
Coordinates 46°15'56.678" N 8°6'13" E