LAGOS, NIGERIA:  With a metropolitan population estimated at 13.6 million in 2016, Lagos now has the second largest population in Africa, after Cairo. The population of Lagos continues to grow rapidly due to high levels of in-migration and birthrates.  Two out of three residents live in substandard housing and lack viable access to clean water, waste disposal, electricity and roads. In 2014, Lagos was the twentieth most populous city in the world, according to UN estimates.

Source:  United Nations,  World Urbanization Prospects, 2014 Revision; ESRI, The Age of Megacities