The largest fertile fossil hominid area in the world between 3.5 – 1.5 million years ago is in South Africa. It is in the Sterkfontein valley near Johannesburg. The 3 sites found here are: Sterkfontein, Kromdraai and Swartkrans.
Sterkfontein Cave Visitor Interpretation Centre, Cradle of Humankind, Gauteng, South Africa
If you want to read more on this subject:
* Link 1
* Link 2
Source: The Archaeology of Southern Africa p.44-45