Will book DMZ tour, but sightseeing other areas, best way to travel, get around
I strongly recommend use city tour bus which wil take you every famous place. In Seoul, you should'nt miss Samshong dong near blue house and Bukchon, Myungdong, Namsan, Dongdaemun & Namdaemun, Insadong and Palace(Kyongbok Palace).
If you have a time to spend a countryside, you'd be better go to Tongyong by train or express bus do not miss Jangsa island..I can't tell you more but Korea has a lot of good things that must see. over 7 years ago