This multiplex observatory just 2km from North Korea offers prime views into the 'hermit kingdom'. Through binoculars (鈧500 for two minutes) you can spy villages, workers in rice fields, military towers and distant mountain ranges. There's a short, introductory video in English, but you'll need to request it to be played.
Bus 26 will get you here, with bus 27 returning to Ganghwa-eup terminal (35 minutes).