Authentic Korean in Arlington?
Go to Annandale; there are a lot of good places to try. It has become known as Koreatown and they have the best Korean resturants in town. Much as Eden Center has the best Viet Namese. Take a look at the Washington article http://www.chowhound.com/topics/177756 or the Chowhourd thread on this topic: http://www.chowhound.com/topics/177756
The favorite of the Korean Embassy is Woo Lae Oak in Pentagon City. I happen to like the newer one that opened in Tysons Corner, but we used to take my son there on his birthday because he loved the cooking at the table thing. Every time I've been in the place, it's usually packed and at least 75% of the patrons are Korean.
Woo Rae Oak is the only Korean restaurant I know of in Arlington, but it is not authentic. There are authentic Korean people working there, but the food is prepared for the Americans and tourists. I went one night, homesick and craving some "soul" food, but it was not meant to be. A big part of Korean food is the banchan (side dishes). I think I got three--limpy soy bean sprouts, spinach, and watered down, un-ripe kimchee. I asked them what was up. They said, Americans don't like spicy food, so we have to cater to their taste. If you like overpriced, hastily-produced American-tailored Korean food, go for it. If the person grew up on Korean food, I'd recommend NOT going there.
The authentic Korean restaurants are going to be in Annandale, but then you'll need a car. There are lots of fantastic ethnic restaurants in Arlington. Woo Rae Oak is not one of them.