They have great export markets-Samsung, LG, Hyundai, Lotte, etc. The Korea shipyards are huge, with 10% of the world capacity-
http://industrial-center.com/Koreanshipyards.html
The bulk of the megaprojects seem to come from Hyundai and Lotte. I've heard rumors that some of the megacorps are partially government backed. Other projects like the Incheon twins and Dream Hub/Tripple1 were governement backed, but the government (perhaps wisely, perhaps not) decided to drop the backing and those projects are dead.
Like Japan, activity/growth is concentrated in the cities, with some depopulation of the countryside.
http://en.wikipedia.org/wiki/Template:Chaebol
http://en.wikipedia.org/wiki/Economy_of_South_Korea
South Korea is also seeing increased tourism from China.