Though many people do not know it, Seoul is one of the world's best tango cities -- the Sinsa area alone boasts 3 different tango venues, and in Seoul it is possible to go to a milonga every night of the week.
Popular tango salons to contact if you're visiting Seoul are:
Just a few of the many places in Seoul to dance Argentine Tango.
The Seoul Tango Festival is the subject of Ray Bartlett's documentary, Tango in Seoul: A Documentary. Currently in production, the film's info page can be found here. Donations large and small are greatly appreciated.