I recommend you some of famous places.
동대문-It's kind of huge shopping town.
인사동-There are lots of traditional arts.
삼청동-This place is something different. Have a pie with ice creams.
홍대- It's around 홍대. There are many clubs and restaurnats.
한강 근처- I forgot the station, BTW nice view.
서울N타워- You can have a look whole Seoul at your sight.
Enjoy your travel in Seoul.
If you have a time, go to 동해(East sea).
You can take a train from 서울역 or 영등포역,
4hrs far from seoul.
I guessssssss....nor sure. ^^sorry