For all the time I spent in the city of Seoul, I was able to make three trips into Bukhansan National Park which is partially inside the boundary of the city. It can be both a remote space, and a space overrun by visitors from the cities around. Seoul contains more the 10 million residents, and the metropolitan region is the third largest in the world with more than 25 million.
The park itself is two mountains, Bukhansan Mountain itself and Dobongsan Mountain, although there are many named peaks along the two ridges. The valley containing the Bukhansanseong fortress divides the two mountains, and is said, due to natural springs, to have had the capacity to hold 50,000 people.

IlJumun Jingwansa was my guide on the south end of Bukhansan Mountain (any history or natural history I get right is due to him — anything wrong is mine). We hiked up onto the side of the Bukhansan of the National Park, between Hyangnobong and Jokduribong peaks. Jingwansa was incredibly knowledgeable about the cultural and natural history, and as we walked and I peppered him with questions which he answered, for biological questions looking up English name equivalents of Latin names where they existed.
We saw two oaks along the way, Quercus acutissima and Quercus mongolica.
We talked about crows and wildfires, trails, and the difficulty of maintaining the natural resources of a park under the constraints of heavy use and a loving public.
These mountains are made of granite, hard, and warm, and dry on the days I saw them. And they overlook the cities around them. It was here that first understood how mountainous Korea is, and something of the relationship between the Korea people, their mountains and their sea. The Korea National Park Service (KNPS) logo reflects this:

More soon… .