Medellin, Colombia offers a window into the future of cities. Once synonymous with the drug violence of Pablo Escobar's murderous cocaine cartel, Colombia's second largest city undergone a remarkable transformation. Medellín has done so largely by investing heavily in upgrading slums and connecting them to the city center. A centerpiece of this effort: innovative public transportation, such as a Metrocable gondola system that helps residents of informal communities get around town and enjoy all the benefits of a reinvented city.