South Korea’s longest fortress snakes along the ridges of Geumjeongsan Mountain, in the city’s northwest. Only parts of the 17km stone wall remain, but the formidable gates have been restored, complete with flags and guard posts. Hikes can begin from any stop north of Dongnae Station (on Metro Line 1). For painless vertical gain, ride a cable car up from near Myeongnyun Station. Just below the highest point (801.5m) is a small shamanist shrine, still in use.