Gwanaksan, the mountain stretching across parts of southern Seoul and Gyeonggi Province, always welcomes hikers of all ages with a total of 15 hiking trails that can be approached from multiple subway stations in Seoul, Anyang and Gwacheon. With its subway-accessible trails, Gwanaksan is one of Seoul's most popular mountains, especially among those in southern Seoul, in any season. This summer, an outdoor swimmi.