Best nightlife in Seoul?

Travel Info
I have an overnight stopover in Seoul on January 18. Where would be the best places to go to soak up the Seoul nightlife? I don't mean just clubs and bars, but any spots in Seoul worth seeing at night and why.

Travel Tips

Nam-San tower. If you want to be in Seoul for stop over. I want to recommend "Nam( it means south)-San( Mountain ) Tower.

Just take a taxi, and say to him. Nam-San-Tower. he will take you there. Don't surprise when he take you to the hill, you got to be on the hill. and also it is quite stiff hill.

After you get there I recomand to be in the restaurant on the top of the tower. (Western style food with good atmosphere.) BECAUSE that restaurant is spinning around very slowly with whole of view with glass. so you can see whole side of city night sight. And some wine as well. ;)

Or take City Tour bus. You can stop anywhere in seoul, get on, get off it is free after get your ticket. and you can just walk around you can watch some movies or shopping( few of stops are right in front of big cinema or etc etc. ).

Or another option, go to Hong-Dae and be soaked up by crazy ppl? lol Well, It is a shi* hol*.

Have fun!

Others
I mainly hangout around gangnam, there are a lot of bars here. Itaewon, by the US base is also popular.
Korean Pride!!
I'd visit downtown
Some of the best times I've had In Seoul have been eating Samgyop sal in an outdoor restaraunts. Samgyup sal is a kind of unsalted bacon. Whatever you do don't slice of the fatty bits thats what gives such a nice taste. You have to be with at least one extra person to go to one of these restaurants. Check out Shincheon or Chongak.
Hongdae and Itaewon seem to be the most popular...Itaewon can be U.S. soldier heavy, whereas the Hongdae area is more university aged students, etc. Those 2 areas are nightlife oriented.
Insadong is more of a cultural/shopping area that's pretty cool, but it's more of a daytime destination.
Apgujeong is a ritzy neighborhood in (Gangnam) Seoul. It has shopping and also a lot of bars and restaurants, but it's expensive. Lotsa fancy cars and pretty girls there.