The Green Line (Swedish: Gröna linjen) is the oldest of the three Stockholm Metro lines. The 41.256-kilometre (25.635 mi) long line comprises a single double-tracked line north of the city centre, splitting into three branches south of the city centre. The first section of the line opened as a metro in 1950, making it the first and oldest metro line in the Nordic countries, although some parts of the line date back to the 1930s and were originally used by the Stockholm tramway.