Gang-nam is a city in South Korea where Psy was raised it translates into English as city south of river it is a business city but Psy claims the style there is dress classy act cheesy
so when Psy says Gang-nam style he means in the style of the people of Gang-nam
South of the Han.
Search maps.Google.com for Coex Mall, Gangnam-gu, Seoul.
<http://maps.google.com/maps?f=q&hl=en&geocode=&q=coex+gangnam-gu,+seoul&ie=UTF8&ll=37.515121,127.059631&spn=0.010297,0.020041&t=h&z=16>
Google Map