Kōshū Kaidō
The station complex extends over a large area, with the Tokyo Metro Marunouchi Line and Toei Shinjuku Line platforms located in Shinjuku 3-chome (after which the station is named), and the Tokyo Metro Fukutoshin Line platforms located in Shinjuku 5-chome. The station concourse on the first basement ("B1F") level is connected to Shinjuku Station in the west by an underground pedestrian passage above the Marunouchi Line, called the Metro Promenade. Another underground passage between the two stations was completed in 2012, situated below the Kōshū Kaidō. The southern end of the Fukutoshin Line platform is linked to the Takashimaya Times Square complex by an underground passageway.