The first line of a new subway system in the South Korean city of Incheon began operations after six years of construction. The initial section of the north-south Incheon Subway Line 1 covered approximately 12 miles between the Bakchon and Dongmak stations. Incheon Subway Line 1, which is also included as part of the Seoul Metropolitan Subway network, now covers 18.3 miles between Gyeyang Station in the north and the International Business District Station (located within the Songdo International Business District) in the south. The opening of Incheon Subway Line 1 made Incheon the fourth city in South Korea with a subway system; the other cities with that means of transportation are Seoul, Busan, and Daegu.
For more information about Incheon Subway Line 1, please check out https://en.wikipedia.org/wiki/Incheon_Subway_Line_1.