I finally visited 'Seoul Forest,' after always just passing by it in cabs. Turns out, it isn't exactly a 'forest', but more like your average Korean park. I have to admit though, it is a good place to nap on the grass, under the afternoon sun, which is exactly what I did this past week. :)
To get there, take the subway Line 2 to Ttukseom Station, Exit #8. Follow the signs to 'Seoul Forest,' about a 15-minute walk.