Jirisan National Park is a chain of mountains and the mountain of the same name is the second largest of Korea.
My suggestion
The climb up Mount Jirisan is difficult and dangerous without a guide, however, there are many more accessible trails in the region. Plan to leave early in the morning because the sun sets very early.
South Korea is fascinating when it comes to cookery: each day after work, Koreans meet up amongst friends in restaurants or street stands to talk and relish low-priced dishes.
Seoul is an ideal place to visit if you want to really get to the heart of Korean culture, in all its strange exoticness! Shops, culture, food, things to see and do: you're bound to find something you'll enjoy during your visit!