Seoul locals... does anyone know where this is?

I keep seeing photos of some kind of market alley in Seoul on Instagram with a retro vibe.
It's a narrow alleyway that doesn't feel sophisticated at all;
instead, it's lined with very old signs—I can't quite remember if they were for shabby old restaurants, hardware stores, secondhand bookstores, or instrument shops.
When it's late at night and there are few people around, it has this kind of atmosphere where you feel like a gangster might be standing there smoking and threatening you.
Does anyone know which area this is?