Antique malls in the US, at least in Georgia and California, seem to be less about true antiques and more about vintage. As such, I enjoyed checking out the stocks from time to time, hunting for bargains on cool old junk. It's like a flea market, but cleaner. Once you get past all the stalls with frilly stuff, crafts, and "antiqued" goods. And if you can see through the overpricing in many of the booths.
Korean antique malls, at least the ones I visited, seem to have real, honest antiques. Or at least good fakes. I don't know how to tell the difference. But I vintage stuff is hard to find, and "recent" vintage doesn't seem to exist here. That's okay, there are other places to find those goods, and I'll tell you about them some other time.
The antique markets carry Korean, Japanese, and other Asian goods, including pipes, hats, locks, paper goods, and more.
From Dapsimni Station on Line 5, take exit 1 or 2 and walk off the main street, starting with the orange tiled building behind the car park. Building #5 to the left is your next stop, with the third building shown on the map, just after the next street. Really, you can't miss them with the goods outside.
To get to Janganpyeong, return to exit 2, but turn left at the main street, walking for about 10 minutes. Janganpyeong is in the brown-tiled arcade with another section behind it. Again, there are lots of statues and other goods outside.
The malls are generally open 10:00-16:30 or later (closed Sundays), though I would try to go in the early afternoon. I think several of the "stores" close earlier, and I believe there are outdoor markets sometimes.