The first thing that came to my mind when I saw this ceremony was "the royal guards sure have a really cool uniform". My eyes were feasting on the colors of fabrics that the guards were wearing. I mean, how can you not, really? Plus they have really cool hats, flags, weapons, and musical instruments too. There are two royal guard changing ceremonies that you see in Seoul, one in Gyeongbokgung Palace (경복궁), and the other one at Deoksugung Palace (덕수궁), which is the one I went to. The ceremony itself took about 20 minutes or so, consisting of the guards marching out of the gate bearing flags and playing traditional musical instruments, the exchange of guards, and the final march accompanied by the traditional musical instruments once again. I would probably recommend checking this ceremony out at least once because it's pretty interesting. Since it's a scheduled ceremony, you can check out the time to see it here before coming to Deoksugung Palace.
Fun fact: I had to get pretty close to the guards to get the low-angle shot and when the head guard saw me squatting in front of him, he stared directly at my camera for a good minute without blinking. He's so cool for being a good sport about it.