Seoul Subway Line 2

Seoul Subway Line 2 (Korean: 서울 지하철 2호선), 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 (48.8 km (30.3 mi)), the Seongsu Branch (5.4 km (3.4 mi)) and the Sinjeong Branch (6.0 km (3.7 mi)) for a total line length of 60.2 km (37.4 mi). The Line 2 loop is the third longest subway loop in the world after Moscow Metro Bolshaya Koltsevaya line and 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.

In 1972, then-Mayor of Seoul Koo Ja-choon [ko] (1932–1996) changed the existing plans for the Seoul Subway to better enable connectivity around the growing Seoul City and allow for development to take place across the Seoul Metropolitan Area. Line 2 was built in 1978–84 together with the Seongsu Branch (the second Sinjeong Branch was built 1989–95). Dangsan Railway Bridge was closed for reconstruction in 1996 and reopened November 22, 1999. The old steel girder bridge was replaced by a 1.3-kilometre (0.81 mi) long concrete bridge between Dangsan on the southern side of the river and Hapjeong on the northern bank. During this period, the inner loop only ran to Dangsan Station, and the outer loop only ran to either Hongik University Station or Hapjeong Station.

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.

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 2011, retailer Homeplus opened the world's first virtual supermarket at Seolleung station, where smartphone users can photograph the bar code of life-size pictures of 500 items of food, toiletries, electronics etc. on the walls and platform screen doors, for delivery the same day.

All stations on all branches are in Seoul.

There is a possible extension currently in the conception stage to extend the Sinjeong Branch to 3.7 km to Gayang Station on Line 9. The path would include a new station named Gangseo-gu Office in between Kkachisan and Gayang.