The Channel Tunnel is a 50.45-kilometre (31.35 mi) rail tunnel linking Folkestone, Kent, in the United Kingdom, with Coquelles, Pas-de-Calais, near Calais in northern France, beneath the English Channel at the Strait of Dover. At its lowest point, it is 75 m (250 ft) deep below the sea bed and 115 m (380 ft) below sea level. At 37.9 kilometres (23.5 mi), the tunnel has the longest undersea portion of any tunnel in the world.
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