Deoksugung is one of the "Five Grand Palaces" in Seoul. Somehow I've been by it a number of times, but only managed to get around to going inside it once after watching the Changing of the Royal Guard. If you've seen some of the other palaces, it might be a bit repetitive, although there are some modern touches to be found, such as a western garden and fountain.
During the Japanese colonization of Korea (1910-1945), the palace was heavily destroyed. It's a period of Korean history I'd love to learn more about, but in general the colonial rule destroyed many Korean artifacts while seeking to forcefully assimilate Korea both politically and economically into the Japanese Empire. It's this colonization that is the source of many elder Koreans animosity towards Japan.
Garden inside of Deoksu Palace.