The Stockholm metro () is a metro system in Stockholm in Sweden. The first line was opened in 1950. However, underground trams had been used since 1933. The system has 100 stations in use, 47 of them are underground and 53 above ground. There are three lines (Green, Red and Blue) travelling through Central Stockholm. In the year of 2013 the Stockholm metro cars totally carried 328 million passengers inside. It corresponds to approximately 898,630 passengers per day.