The Fréjus Rail Tunnel (also called Mont Cenis Tunnel) is a rail tunnel of 13.7 km (8.5 mi) length in the European Alps, carrying the Turin–Modane railway through Mont Cenis to an end-on connection with the Culoz–Modane railway and linking Bardonecchia in Italy to Modane in France. Its mean altitude is 1,123 metres (3,684 ft) and it passes beneath the Pointe du Fréjus (2,932 metres (9,619 ft)) and the Col du Fréjus (2,542 metres (8,340 ft)).
Headed by the Savoyard civil engineer Germain Sommeiller, construction of the tunnel commenced during August 1857, at a time when both ends of the future tunnel were in the Kingdom of Sardinia. From the onset, the tunnel was an ambitious engineering challenge, its gallery being twice the length of any tunnel previously constructed. Some figures believed that it would take as many as 40 years to complete; the total construction time was 13 years, the work having been greatly accelerated by the introduction of new technologies such as pneumatic drilling machines and dynamite. On 17 September 1871, the Fréjus Tunnel was opened to traffic for the first time, facilitating a new era of interaction between France and Italy.
