Marunouchi Line

The Marunouchi Line (丸ノ内線, Marunouchi-sen) is a subway line in Tokyo, Japan, operated by Tokyo Metro. The line runs in a U-shape between Ogikubo Station in Suginami and Ikebukuro Station in Toshima, with a branch line between Nakano-Sakaue Station and Hōnanchō Station. The official name is Line 4 Marunouchi Line (4号線丸ノ内線, Yon-gō-sen Marunouchi-sen). The Marunouchi Line was the fourth subway line constructed in Japan, following the Osaka Municipal Subway Yotsubashi Line. Its design is similar to that of the Ginza Line, the oldest subway line in Tokyo and in Asia. Both lines are standard gauge and use third rail power, unlike subsequent Tokyo subway lines which use overhead wires and are mostly narrow gauge to accommodate through services with other railway lines. The line's name is derived from Marunouchi, a district in Chiyoda. It was adopted in 1953 by the Teito Rapid Transit Authority, the operator at the time. Prior to this line, a Tokyo tram line of the same name (opened in 1921) operated above ground between Tokyo and Ōtemachi, along the route of the present line. On maps, diagrams and signboards, the line is shown using the color red, and its stations are given numbers using the letters "M" for the main line and "Mb" for the branch line.