Tatu City outside Kenya's capital is a start-up city, privately owned and with aspirations of eventually having a population of 250,000. There are similar projects around the world. But in sub-Saharan Africa, champions hope that new-city developments can address the continent’s urbanization conundrum: While the growth of cities has rolled back poverty across the world, the region has largely been an exception. Sub-Saharan Africa is urbanizing while still poor. The region lacks the capital needed to transform cities into engines of economic growth. Some experts consider Tatu City with its new infrastructure and strict rules to be a model. (AP video by Jackson Njehia)