A perfect weekend for Lee Jeong-eun, a 35-year-old office worker, is not about striding in shopping malls to grab the last summer dress on sale, having her nails done or watching the latest Hollywood blockbuster in an air-conditioned movie theater. All she has to do is to go to a campsite in Jamsil Park, one of 12 parks open on the banks of the Hangang river. A book, a bottle ..