The city's main attraction is the fortress, dating from the 18th century, and whose ramparts are quite impressive.
My suggestion
You are allowed to go into some of the buildings upstairs. Take off your shoes, and rest for a little while, enjoying the coolness of the buildings in complete contrast to the heat prevalent outdoors as from the month of May.
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!