Hannam has the best foreign market in Seoul.  Go to Hangangjin Station (항강진역) and leave through exit 2.  Head straight under the highway.  Cross the footbridge and follow the street right.  Look for a Volvo building on your left.  Head downstairs and you're there!  Be sure to check all three markets in this building for what you want.  There is one large one, one that is like a small deli, and one that looks more like a gas station market than anything else (but they have some great ingredients that you can't find anywhere else.  Almond extract for instance.).

Hanam is a city in Gyeonggi Province, South Korea . Formerly a part of Gwangju County, it was designated a city in 1989. The ancient Baekje capital of Hanam Wiryeseong may have been located there. Lying immediately east of Seoul , Hanam is also bordered by Namyangju , Gwangju , and Seongnam .

I think this is where "nam han san sung" is at. The road to this place is very curvy. There are some good resturants that specialize in spicy-chicken-and-potatoes known in Korean as "Dak doh ree tang". Worth a visit just for the food alone. Enjoy the lovely scenic drive also. This is a recollection from the early 90's so your experience may vary.

Horrible Traffic. Takes 1 and half hour to travel 55KM.