M4 is one of the 4 lines of metro of the Bucharest Metro. M4 Line runs from Gara de Nord to Parc Bazilescu. This line is the shortest (6.30 Km) of those of the Bucharest Metro and the most recent (the first stations on this line opened on March 1, 2000 and the last two opened on July 1, 2011).
Another two stations (Laminorului, Lac Străuleşti) are going to be built in the near future.