By 2025 one percent of the world 's urban population will live in megacities says the UN . Megacities can bring not just wealth and employment but also cultural benefits , says the United Nations . The most populous megacity is Brazil in Brazil , with 21 to inhabitants . Megacities in countries like India and Brazil will grow fastest over 2025 .
By 2025 one percent of the world 's urban population will live in megacities says the UN . The most populous megacity is Brazil in Brazil , with 21 to inhabitants . Megacities in countries like India and Brazil will grow fastest over 2025 .