Being in Korea for almost three months has taught me all I will ever need to know about mountains. The landscape of Seoul is especially hilly, and I have found myself spending a considerable amount of time walking up the city's inclines and stairs.
Being in Korea, I have spent more time walking up hills and stairs than I have my entire life. Most of South Korea is mountainous, and Seoul is no exception. In Seoul, you'll find it is very easy to break away from the city, as there are various mountains and parks to explore.
For a long time, the mountains and unforgiving climate of Korea worked to people's advantage in terms of security. Historically, Seoul utilized its four surrounding mountains (Baegaksan, Naksan, Namsan and Inwangsan) by setting up a city wall along their ridges. The mountains, the wall and the distance outsiders needed to travel played a major hand in keeping potential intruders out of the city.