Seoul is literally surrounded by mountains and the best way to get a good overview of it is to climb over Namsan, the mountain in the very heart of the city, even if the smog prevents the sky from ever being completely blue, you'll still find yourself in awe at the beauty of nature and surely you can't leave the city before a trip to Bukhansan national park in the northern part of the city for some hiking activities. Very few cities in the world, especially one that counts over 24 millions inhabitants can boast such a wonderful natural location.