From 1868 to 1871, the Mont Cenis Pass Railway worked as a temporary link over the Mont Cenis Pass. It was closed soon after the Fréjus Railway opened.
Once "Savoy became part of France, the Fréjus Tunnel became a possible invasion route from Italy to France, avoiding the difficulties of the "Mont Cenis pass. Accordingly, an extraordinary amount of fortification was placed around Modane. The "Fort du Replaton and the "Fort du Sapey were built in the late 19th century on the heights across the valley of the Arc. In the 1930s the "Maginot Line fortifications "Ouvrage Saint-Gobain, "Ouvrage Saint-Antoine and additional fortifications at "Le Sappey were built.
A blockhouse along the rail line to the east of the modern tunnel entrance has become a tourist attraction. The maison penchée ("leaning house") was built in 1939 to guard the tunnel entrance over an ammunition magazine connected to the tunnel by a gallery. In 1944 the retreating Germans exploded two rail wagons inside the tunnel entrance, causing the magazine to explode and blasting the blockhouse off its foundations, landing on a tilt.
The original monumental entry on the French side of the tunnel at Modane is now a minor tourist attraction, having been bypassed in 1881 in favor of a new entrance somewhat to the east in more stable ground. A steam locomotive has been placed in the old entrance, which is now located along a roadside.
"Gotthard Rail Tunnel