The colors of korean forests in fall are surely the most beautiful that can be found in korean landscapes. If you are in Seoul in october, you should absolutly visit the northern mountains of Bukhansan or the amazing fortress of Namhansanseong in the south. If you are quite short of time, Namsan is then probably the best option you have. Located in the heart of Seoul, the small mountain is like a massive green giant surrounded by thousands of dark buildings.
The above picture has been taken in a walkway in Namsan, and As you can guess, it has of course been edited. Yet, the main correction has simply been to remove all colors except the red and orange ones. The result really surprised me. The high contrats and red colors of the trees immidiately gave me the impression that the whole forest was in fire.