How the violent barrios of Medellin were transformed

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Medellin used to be one of the world's most dangerous cities, with a sprawling network of slums and a serious crime problem fueled by drug trafficking. During the 1990s, there was a dramatic transformation. A leading architect involved in the project, Carlos Alberto Montoya Correa, describes how the regeneration took place. Photo: Medellin viewed from a cable car Credit: Getty Images