7. Lagos, Nigeria
Above, a congested street in Lagos sprawls to the horizon. Lagos may slightly trail Bamako in the rate of its urban population growth, but the Nigerian economic capital dwarfs its West African rival in size and vitality. The city proper had nearly 10 million people in 2010, and is projected to reach 15 million by 2015, with a growth rate of 4.44 percent. Within a couple years, it will eclipse Cairo as the largest city in Africa.
ClaudiaNapoli via Flickr