Africa, the world’s second-largest continent, is home to nearly 3,000 separate ethnic groups spread across 11.7 million square miles (30.3 million square km). While Africa boasts many densely populated urban areas, most other areas remain rural with limited infrastructure. Farming is the primary occupation of most Africans, although many people living in areas rich in natural resources, such as diamonds and coal, are employed by large mining companies and related industries.