I hope you've seen Michelle's beautiful pictures on Gostiniy Dvor, if not here's the link. I did a little video on my review of the place. The restaurant is located at Dongdaemun Culture and History Museum: 동대문역사문화공원 (Subway line 2,4,5). Sorry I said the wrong subway line in the video. It's right out exit 7 and go down the alley and look for a red sign with Russian writing.
So does it have the best food in Seoul?
Not so much, but I love the ethnicity of it. The night that I went, I kept on hearing the microwave go off. I guess it was a slow night (Wednesday) and we were the only table in the restaurant, but I didn't feel like all the food was the best. I mean some things will microwave well (i.e. the stuffed cabbage, but somethings won't POTATOES!). The smoked herring is a dish I wouldn't recommend. It needs to be smoked longer- it had the texture of old bubblegum. The dishes they do very well are the borscht, the dumplings, and the stuffed cabbage. Oh, and I don't recommend the french fries (I didn't order them). The oil wasn't hot enough, so the fries came out very greasy.
Now, would I go there again? Of course. The beers and the vodka are excellent and I love that I can get authentic Russian food in Seoul.