I was wrong about Incheon being totally industrial. I decided to walk towards the closest looking hill; it was only a 20 minute walk. Much to my delight, there was a hiking trail, so I started up. The trail branched into two paths - one wide and gentle, the other narrow and steep. I walked up the narrow path, getting a real workout in the process. It was maybe 25 minutes before I reached the top; there was a clearing, and you could look out in every direction. The city surrounds this hill, and stretches on and on in every direction. I could see the massive international Incheon harbour, and multiple other clearings on hills - trails connect them all.
Next weekend, I'll make a day of it - see how many hills I can walk.
And yes, photos of these views will be forthcoming.