From Gyeongbokgung Station line 3 subway to Seoul Nambu Bus Terminal then bus to Seosan. 2hrs 37min ₩9,917. From Seoul Station train to Gimpo Airport, walk to Gimpo Airport, then bus to Seosan. 3hrs 23min ₩17,116. From Seoul taxi to Seosan. 1hrs 25min ₩162,508. From Seoul drive to Seosan. 1hrs 25min ₩23,098.