The fortress is still quite intact: a lot of different towers, four gates, and the city wall can be seen today. The best thing to do is walk the city walls - then you pass all sights. This tour is about 5.5 kilometers long but will take you an hour or two because of the steep climbs involved.
Because of the burning heat on the day I visited the site, I did only half of the tour. Still worthwhile though: as most of the monuments I visited in Korea it is renovated very well.