Changdeok Palace was the second major palace buit in Seoul, after Gyeongbok Palace, which you can see pictures of here. While it was originally completed in 1402, much of it has been destroyed during various wars and occupations. Some structures, such as a bridge are original from the 1400s, others restored like the main gate in the 1600s while the vast majority were rebuilt after World War II and the Korean War.
The main hall seen above is much like many of those seen in other Korean palaces. Truthfully, while quite nice and a UNESCO World Heritage Site, there isn't much that sets Changdeok Palace apart from any of the other 4 grand palaces in Seoul.
On the right on the above image you can see two rock viewing installations, there were a few scattered around the main grounds. Called suseok in Korean, this was the first time I'd ever seen such a thing. At first, I thought it was pretty funny to see rocks put up on a pedestal like that, but after seeing a few I stopped to look at them and most were actually amazing shaped.
The most unique aspect of Changdeok is the rear garden. Only accessible by guided tour, it was originally off limits to anyone but the royal family and their consorts. It is a beautiful wooded area that blocked out much of the sun, leaving greens and browns in all directions. Unfortunately, due to the only access being via guided tour, the tour itself was a bit crowded.