Nitrox,stay at the Continental as apart from the high standard you can enter the Mall from within.There are restaurants,movie houses,banks etc.You could spend the whole day without going out.Also they arrange day tours(2/3 hours)where they take you to the diamond mines,Mendelas residence and Pretoria.They also take you to the safe shopping area where you can buy artifacts etc.Mind you JoBurg is a dangerous city and you do not go around alone down there.