quality:correction
The Stockholm Metro is a rapid transit system in Stockholm, Sweden. The first line opened in 1950 as the first metro line in the Nordic countries, and today the system has 100 stations in use, of which 47 are underground and 53 above ground. There are three coloured lines, as shown on the metro maps, which form seven numbered routes with different termini. Routes numbered 17, 18 and 19, 13 and 14 and 10 and 11 all go through the centre of the city, resulting in a very centralized system. All three lines and seven routes interchange at T-Centralen station. Apart from this, there are three other interchange between lines, at Fridhemsplan, Slussen and Gamla stan stations. The metro is equipped with ticket gates. Single tickets may be bought in advance, typically in privately owned smaller shops, on the web, or at ticket machines that are available in all underground stations and on several tram, bus, or boat stops. Tickets are also available at the ticket booth by the gates to the metro, or passengers can use contactless payment with any Visa, Mastercard or American Express payment card. In 2019, the metro carried 462 million passengers, which corresponds to 1.265,9 million in a normal weekday. The 105.7-kilometre-long (65.7 mi) metro system is owned by the Stockholm County Council through the company Storstockholms Lokaltrafik (SL). The operation has been contracted to MTR since 2 November 2009. The Stockholm metro system has been called 'the world’s longest art gallery', with more than 90 of the network's 100 stations decorated with sculptures, rock formations, mosaics, paintings, installations, engravings and reliefs by over 150 different artists. The Stockholm Metro is the only metro system in Sweden; Gothenburg seriously studied the idea of converting its tram system into a metro in the 1960s, but abandoned said idea after it was deemed prohibitively expensive to tunnel under the city's soils, which are partially made up of clay.