High Quality Content by WIKIPEDIA articles! The Gyeongbu Line (Gyeongbuseon) is the most important railway line in South Korea and one of the oldest. It was constructed by Japan in 1905, connecting Seoul to Suwon, Daejeon, Daegu, and Busan. The Gyeongbu Line is by far the most heavily travelled rail line in South Korea. High-speed, express, local, and freight trains provide frequent service along its entire length.