Countries everywhere are divided into two distinct spatial realms: one urban, one rural. Classic models of development predict faster growth in the urban sector, causing rapid migration from rural areas to cities and raising average incomes in both realms. South Africa faces an unconventional challenge in that it has symptoms of a spatial realm that is not rural and not fully urban. In many ways, South African townships--and especially informal settlements--are similar to slums in the developing world, although never was a slum formed with as much central planning and purpose as were some of...