Seoul Subway Line 2 (), also known as the Circle Line, is a circular line of the Seoul Metropolitan Subway. The line running clockwise is called the "inner circle line" and the counter-clockwise line is called the "outer circle line". This is Seoul's most heavily used line, and consists of the main loop (), the Seongsu Branch () and the Sinjeong Branch () for a total line length of . The Line 2 loop is the second longest subway loop in the world after Beijing Subway Line 10. In 2019, Line 2 had an annual ridership of 812 million passengers or 2.2 million passengers per day. Headways on the line vary from 2 minutes 18 seconds on peak periods and 5–6 minutes off-peak periods. The line connects the city centre to Gangnam, Teheran Valley and the COEX/KWTC complex. History Line 2 was built in 1978–84 together with the Seongsu Branch (the second Sinjeong Branch was built 1989–95). Dangsan bridge was closed for reconstruction in 1996 and reopened November 22, 1999. The old steel girder bridge was replaced by a long concrete bridge between Dangsan on the southern side of the river and Hapjeong on the northern bank. Yongdu station on the Seongsu Branch (between Sindap and Sinseol stations) is the first station in the Seoul Subway system with operating platform screen doors. As of 2008 platform screen doors are operating at all stations along Line 2. New rolling stock has also progressively came on line, replacing older vehicles. October 31, 1980: Sinseol-dong – Sports Complex (via Seongsu) section opened December 23, 1982: Sports Complex – Seoul Nat'l Univ. of Education section opened September 16, 1983: Euljiro 1-ga – Seongsu section opened; Sinseol-dong – Seongsu section separated as Seongsu Branch December 17, 1983: Seoul Nat'l Univ. of Education – Seoul Nat'l University section opened May 22, 1984: Seoul Nat'l University – Euljiro 1-ga (via Sindorim) section opened; Circle Line completed May 22, 1992: Sindorim – Yangcheon-gu Office section opened as Sinjeong Branch February 29, 1996: Sinjeongnegeori Station opened as extension of Sinjeong Branch March 20, 1996: Kkachisan Station opened as extension of Sinjeong Branch October 20, 2005: Yongdu Station opened on the Seongsu Branch Facilities In December 2010 the line is recorded as having the highest WiFi data consumption in the Seoul Metropolitan area. It averaged 2.56 times more than the other 14 subway lines fitted with WiFi service zones. In