The Wits Art Museum on the University of the Witwatersrand campus has a strong collection of southern African traditional and contemporary art. The highlights are the traditional beadwork — among the finest collections of Zulu and Ndebele beadwork in the country — alongside carved wooden figures, masks, and ceremonial objects from across the region. The temporary exhibitions are consistently worth checking.
Entry is free, which makes it an easy addition to a day in the inner city. The university campus is accessible and safe during the day. The museum is compact enough to cover in an hour and a half, and the traditional arts collection in particular is worth the time even if modern art is not usually your interest — the beadwork is formally extraordinary and the explanatory labels are good. It is close to Braamfontein and Newtown if you are combining several inner-city stops.