The Marmaray Tunnel (Turkish: Marmaray Tüneli) is a 13.5 km (8.4 mi) long undersea railway tunnel in Istanbul, Turkey, beneath the Bosporus strait, linking Kazlıçeşme, Zeytinburnu in Europe with Ayrılıkçeşmesi in Asia. The tunnel consists of two single track tunnels with three underground railway stations: Yenikapı, Sirkeci and Üsküdar.