The Moscow Metro (Russian: Московский метрополитен, IPA: [mɐˈskofskʲɪj mʲɪtrəpəlʲɪˈtɛn]) is a rapid transit system serving Moscow, Russia, and the neighbouring Moscow Oblast cities of Krasnogorsk, Reutov, Lyubertsy and Kotelniki. Opened in 1935 with one 11-kilometre (6.8 mi) line and 13 stations, it was the first underground railway system in the Soviet Union. As of 2019, the Moscow Metro, excluding the Moscow Central Circle and Moscow Monorail, has 232 stations (263 with Moscow Central Circle) and its route length is 397.3 km (246.9 mi), making it the fifth longest in the world. The system is mostly underground, with the deepest section 84 metres (276 ft) underground at the Park Pobedy station, one of the world's deepest underground stations. It is the busiest metro system in Europe, and is considered a tourist attraction in itself. The Moscow Metro, a state-owned enterprise, is 381 km (237 mi) long and consists of twelve lines and 223 stations organized in a spoke-hub distribution paradigm, with the majority of rail lines running radially from the centre of Moscow to the outlying areas. The Koltsevaya Line (line 5) forms a 20-kilometre (12 mi) long circle which enables passenger travel between these diameters, and the new Moscow Central Circle (line 14) forms a 54-kilometre (34 mi) longer circle that serves a similar purpose on middle periphery. Most stations and lines are underground, but some lines have at-grade and elevated sections; the Filyovskaya Line, Butovskaya Line and the Central Circle Line are the three lines that are at grade or mostly at grade. The Moscow Metro uses the Russian gauge of 1,520 millimetres (60 in), like other Russian railways, and an underrunning third rail with a supply of 825 V DC, except line 13 and 14. The average distance between stations is 1.7 kilometres (1.1 mi); the shortest (502 metres (1,647 ft) long) section is between Vystavochnaya and Mezhdunarodnaya and the longest (6.627 kilometres (4.118 mi) long) is between Krylatskoye and Strogino. Long distances between stations have the positive effect of a high cruising speed of 41.7 kilometres per hour (25.9 mph). The Moscow Metro opens at 05:25 and closes at 01:00. The exact opening time varies at different stations according to the arrival of the first train, but all stations simultaneously close their entrances at 01:00 for maintenance, and so do transfer corridors. The minimum interval between trains is 90 seconds during the morning and evening rush hours. As of 2017 the system had an average daily ridership of 6.99 million passengers. Peak daily ridership of 9.71 million was recorded on 26 December 2014. Free wi-fi has been available on all lines of the Moscow Metro since 1 December 2014. The network was launched by MaximaTelecom.