Outdoor Exercise in Korea

outdoor hiking is huge in Korea, and easily (ironically, or strangely) subway accessible.

http://guidetokorea.wordpress.com/2011/12/07/exercise-and-korea/

You should ask your hosts to point you in the direction of the nearest nice, medium outdoor hiking site - they're beautiful, unlittered, and you can even take water bottles and fill up in the natural spring water. Have fun!