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Future cities: Mayors dream big, redefine urban living

By <strong>Natasha Maguder, Leila Hussain, CNN</strong> and<strong> Jenny Soffel</strong>, for CNN <!-- -->
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</br>With more than half the world's population living in a city, mayors are well positioned to help build a sustainable future. As part of CNN's "The City," mayors from Johannesburg to Seoul reveal one bold change they're making in their city. While each city has it's own unique identity, all mayors have the same goal: To make their city smarter, greener and cleaner.

By Natasha Maguder, Leila Hussain, CNN and Jenny Soffel, for CNN

With more than half the world's population living in a city, mayors are well positioned to help build a sustainable future. As part of CNN's "The City," mayors from Johannesburg to Seoul reveal one bold change they're making in their city. While each city has it's own unique identity, all mayors have the same goal: To make their city smarter, greener and cleaner.