The Stockholm metro (, literally: Stockholm's Tunnel Rail) is a metro system in Stockholm, Sweden. The first line opened in 1950, and today the system has 100 stations in use, of which 47 are underground and 53 above ground. There are seven lines—17, 18 and 19 (Green), 13 and 14 (Red) and 10 and 11 (Blue)—going through the Stockholm City Centre. In 2013, the metro carried 328 million passengers, which corresponds to approximately 898,630 riders per day.