The Istanbul Metro (Turkish: İstanbul Metrosu) is a rapid transit railway network that serves the city of Istanbul, Turkey. It is operated by İstanbul Ulaşım (Istanbul Transport), a public enterprise, controlled by the Istanbul Metropolitan Municipality. The oldest section is the metro is M1 line, which opened in 1989; it now includes 70 stations in service, with 30 more under construction. The system currently consists of five lines named M1, M2, M3, M4, and the M6 Mini-Metro.