Seoul has 4 red-light districts: the largest one is "Chongnyangni 588" (located nearby Chongnyangni station), followed by Miari and Yeongdungpo. A fourth red-light district worth mentioning is Itaewon which is mostly frequented by foreigners and is considered to be the low of the low. On the bright side, prostitution in Seoul has been decreasing at a rapid pace since September 2004, when a new law against prostitution was passed and is being strictly enforced.
For instance, in "Chongnyangni 588" the number of brothels diminished by almost threefold to 60 from more than 150 just a few years ago. Further, the land of this district has been bought in 2006 by the Seoul metropolitan government in order to build a highway in the area which is expected to destroy the remaining brothels. The amount of prostitution in the other red-light districts of Seoul has also diminished significantly in the last couple of years.
Although frequenting these places is not recommended for moral and legal reasons alike, it is nonetheless interesting to document what is happening in the red-light districts, if only because some are on the verge of extinction. Here are some typical numbers as of 2004 (1,000 wons = 1 $US). More information on prostitution activities and costs in Korea can be found here.