Korea - [B]Suggestions for Seoul this summer[/B]

I'll be traveling to Seoul this summer. I'll have two nights on the way to Mongolia and four nights returning, late July, early August. Does anyone have suggestions for don't miss sights, things to do? I like hiking, temples, culture, food, just about anything, even wandering around.

The only place I really went to in Seoul was the Gyeongbok Palace (http://en.wikipedia.org/wiki/Gyeongbokgung) that housed the Korean Emperors. Beside that, I ate a lot of Korean BBQ and drank a lot of Soju.

drew