Lying 50 km from Johannesburg, Pretoria, with its peaceful town feel, is actually South Africa's de facto capital.
My suggestion
In contrast to its neighbour Johannesburg, the interesting places to see in Pretoria are all located close to each other. Take advantage of the relative safety of this city to explore it on foot.
The Kruger National Park in one of the best known game reserves in the world, where you'll see a host of wild animals. Among them, you'll be able to spot the Big 5.
Even though Robben Island and Mvezo provide poignant links to Nelson Mandela, spending time exploring his history in Johannesburg will also show you how Madiba spent several years.
Stretching well over 200km, the Drakensberg range is a mind blowing blend of peaks and troughs. Numerous trails run along the length of this hiking paradise.
Durban is the biggest town in KwaZulu-Natal. Sitting on the Sunshine Coast, by the Indian Ocean, its American/Australian beach culture attracts surfers and water sports fans from all over the world.