First of all, Duksugung has the main gate named Daehanmun. It was not maingate and Inwhamun was the main gate. But the road in front of it was too narrow. So they change it into Daehanmun that faced east.

Secondly, Seokeodang is the two-storey building. One time Inmok, Queen Mother was locked in Seokeodang because of King Gwanghaegun's order. And it was made because of Seongjong's older brother. His brother was a crown prince but Seongjong became the king. So he was sorry and give him this house. 

Lastly, Jeonggwangheonhas special style of building because they mixed the style of Korea and western. It was the place where Gojong drank coffee. It was made by the architect a Russian.

In conclusion, Duksugung has many special buildings or styles. I think it would be the large amount of history in Korea.