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. By integrating the city's plumbing and transportation into the barrios, renovating the homes of tens of thousands of families and creating open public spaces, the city has been transformed.

Fi Glover returns with Dr Ellie Cosgrave, director of UCL City Leadership Laboratory and urbanist professor Greg Clark to look for the most inspirational cities, from those tackling environmental issues and urban violence. This week they consider Morocco’s urban development model.

(Photo: The Metrocable in Santo Domingo Savio neighbourhood, in Medellin, Colombia. Credit: Getty Images)