More than half of the world's population currently lives in urban areas. And the forecast is that in the next ten years, another 1 billion people will move to the world's metropolises. In total, the UN-Habitat Global State of Metropolises 2020 report predicts that 3.47 billion people will live in these regions, 39% of the world's population. A reality that must make these metropolitan areas a key player in global governance.