Google maps does have the streets of Seoul, it just doesn't understand the address.
Ah ha, found them. I went to 157-33 Samseong-dong, Gangnum-gu, Seoul, Korea 135-090. I then had to disambiguate to 503 Teheran-ro and remote walked the streets checking out buildings that looked right. It was very near the place Google took me to start, near a CitiBank. [Edit:] There's also a building under construction right across the street, which might help if you're searching for it as I did.
Now if only I can figure out how to share the info without requiring someone to do the same...
[Edit 2:] Well I don't see how to share the view easily. If you go to the address I listed and look N at that address, simply turn to the right to face E and look for a tall white cellular looking building down the street (I think it's 3 doors down the street from the address given).
Anyway, that address will get you in the neighborhood if you want to look for ad space. It's a shame the barriers for the construction site can't be used. Maybe some street art. In a quick perusal I see a VISA ad that appears to be in the process of being put up immediately to the E of NCSoft itself (the site looks like it might belong to the Cadillac dealer just to the E of that and there's an ad with an American flag motif right above the VISA ad, it's blocked by trees and I don't read Korean, so I'm not sure what it is).
[Edit 3:] The address Google has for NCSoft appears to be 158-16 Samseong-dong (509 Teheran-ro), Gangnam-gu, Seoul, Korea 135-090. (Going there puts you in a narrow side street to the W of the bldg, so you have to "walk" S to the main street then turn around to look N.)
