I still don’t know how to pronounce this word, but Ssamziegil is definitely the best place in Insadong. It’s a culture centre with lots of art, craft and other stores. The things they sell there are usually not the ones you can find in the many tourist shops of Insadong.
The whole place has an alternative feel. For example, there are four floors but you don’t need to climb stairs (although you can, and there’s an elevator as well) since you basically walk upwards. The goods you can buy there are not cheap, however.
On the top floor are restaurants and a platform where you can get a nice view over Insadong.
There are always new things to discover, e.g. the decorations on the wall.