This neighborhood is only 5 minutes walk from my house. I often walk through here when I walk to Dongdaemun or stroll through on a boring weekend afternoon. It's a neighborhood where you can find nearly anything used at very cheap prices.
Here's what I found at the Seoul Folk Flea Market:
Then I walked on towards Dongmyo. Here is the actual Dongmyo. It's a shrine dedicated to a Ming dynasty Chinese commander named Guan Yu. It was built mostly to placate the Chinese, though, and Korea was rather indifferent to this shrine and a few others built for the same purpose until the Qing dynasty rose in power and Korea incorporated these shrines out of contempt for the Qing dynasty.
There's not much to see here and I wouldn't recommend going out of your way to come here. The photo below was taken through the grates of a fence. You can not enter the main shrine area. People seem to only come in here to use the public toilet.
The area around Dongmyo is full of all kinds of interesting shops, indoors and outdoors.
I spent about an hour and a half walking around here today, I could have spent 3 hours if I had had a friend to walk around with. I haven't found exactly what I'm looking for yet, but I got lots of good ideas. I'm going to go back with the boyfriend to try to negotiate some prices next time.
To find the Dongmyo outdoor flea market, go to Dongmyo Station exit 3 and walk toward Dongmyo shrine. The market is usually set up all around the shrine area. To find the Folk Flea Market, go to Sinseol-dong station exit 10, turn left at the intersection and walk for about 3 minutes. The Folk flea market is in a large building on a side street before you reach the cheonggyechon stream.