The Simplon Tunnel is a railway tunnel that connects Brig in Switzerland to Domodossola in Italy. It stretches approximately 19.8 kilometers (12.3 miles) and was completed in 1906. The tunnel significantly reduces travel time between the two countries and is an essential part of the European rail network. Constructed through the Alps, the Simplon Tunnel was a remarkable engineering feat of its time. It was initially built to facilitate trade and passenger transport, enhancing economic ties between Switzerland and Italy. Today, it remains a vital route for both freight and passenger trains.