$ 153 million the 20th anniversary of the opening of Arup . The 24.5-kilometer Kisarazu in Folkestone is the world 's longest road tunnel . At 646.7 meters below sea level Fast fact the Seikan Tunnel is the longest and deepest rail tunnel in the world .
$ 153 million the 20th anniversary of the opening of Arup . The 24.5-kilometer Kisarazu in Folkestone is the world 's longest road tunnel . At 646.7 meters below sea level the Seikan Tunnel is the longest and deepest rail tunnel in the world .