When we were there, we stumbled across a partial underground flea market that was mostly new merchandise and actually had little shops set up in the entrance and it was huge. It was in "old Charleston". This was several years ago and I dont know where it was. We parked at the visitors center and just started walking around - when it rained we ducked into a little restaurant to stay dry and had the best shrimp EVER. Maybe you can search online and find things like this. The city should also have a tourism site with information.