What was so cool about it? How much time do you need? Nothing worth seeing in ICN itself?
Typically a category 4 Park Hyatt is enough to make me spend the night if there is kosher food around
From my research, and I may be wrong Seoul isn't such a cool city, although for a night it could be worth it. The DMZ is cool because you get to see all these soldiers driving around in tanks securing this famous border. The history is kind of cool as well. We went to this empty train station which was just built in hope of reunification and it was interesting.
We also went to some Korean restaurant and go to watch all the locals eat their food on the floor with the shoes lined up neatly outside.