Johannesburg also known as Jozi, Jo'burg or Egoli, is the largest city in South Africa, by population. Johannesburg is the provincial capital of Gauteng, the wealthiest province in South Africa, having the largest economy of any metropolitan region in Sub-Saharan Africa. The city is one of the 40 largest metropolitan areas in the world, and is also the world's largest city not situated on a river, lake, or coastline.
The city is the source of a large-scale gold and diamond trade, due to its location on the mineral-rich Witwatersrand range of hills. Johannesburg is served by O.R. Tambo International Airport, the largest and busiest airport in Africa and a gateway for international air travel to and from the rest of Southern Africa. More recently Lanseria International Airport has started international flights, and is situated conveniently on the opposite side of the metropolis.
The Gauteng province as a whole is growing rapidly due to mass urbanisation, which is a feature of many developing countries. According to the State of the Cities Report, the urban portion of Gauteng – comprising primarily the cities of Johannesburg, Ekurhuleni (the East Rand) and Tshwane (greater Pretoria) – will be a polycentric urban region with a projected population of some 14.6 million people by 2015.