Vizzavona tunnel
The Vizzavona Tunnel is a railway tunnel of the Chemins de fer de la Corse on the island of Corsica near Vizzavona . The structure is 3,916 meters long and has a consistent gradient of two percent towards the southwest. This type of construction is very unusual, as only the counter-site driving method is possible for the construction of tunnels of this length . Since both straightening tunnels usually have a slope towards the exits in order to be able to discharge the groundwater that enters during construction , tunnels typically have an apex in their middle . Due to its unusual design with a constant gradient, it is possible with the Vizzavona tunnel to be able to look from one portal of the tunnel to the opposite portal. The northern tunnel entrance is 906 meters above sea level, the highest overburden to the surface of the earth is about 300 meters.
The construction work, which began in 1880, was made more difficult by penetrating water, so that the first train could only enter the tunnel on July 14, 1889.
The Vizzavona tunnel is the longest railway tunnel in France that is used by a narrow-gauge railway .
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Coordinates: 42 ° 7 '43 " N , 9 ° 7' 57" E