関門海峡
The Kanmon Railway Tunnel, Kanmon Roadway Tunnel, and Shin-Kanmon Tunnel are undersea tunnels crossing the Kanmon Straits between Shimonoseki, Yamaguchi, and Kitakyushu, Fukuoka in western Japan. When opened in 1942, the railway tunnel provided the first direct link between Honshu and Kyushu, two of Japan's four main islands.