There are 5 Royal Palaces in Seoul. The entrance for each palace is 3,000 won but if you are wearing the traditional Korean Hanbok, you can enter the palace for free. There is the change of guard ceremony at 10 am and 2pm at the entrance of the Gyeongbokgung Gate. This should be in your definitely must watch list. I found out that these people are not real guards. They are employed by the tourist board to entertain the tourists.