The majority of the world is now urban.Cities are attracting people because they are centers foreconomic activity and can offer a higher quality of life:there are more jobs, more services available, transportoptions to move within the city, trade, knowledge exchange,and connections to other cities and countries. As a result,in 2050, two-thirds of the world population is expected tolive in cities. Cities around the world are implementinginnovative ideas to efficiently manage urbanization. Theyare facing challenges head on and placing themselves on apath toward sustainability. Increasingly, city governmentsare becoming empowered administratively and financially tobe able to serve their growing populations, offering goodpublic transport options, access to clean water, effectivewaste management, and other essential basic services. Thisbooklet of case studies showcases cities in developingcountries that are implementing bold ideas with theobjective of achieving environmental, economic and socialsustainability. In all the stories included, the World BankGroup has been able to work alongside the cities to helpthem meet their goals by offering a number of services.These case studies show what a wide variety of cities haveachieved in this endeavor, with clear and measurableresults. Cities have responded to the new challenges andopportunities of rapid urbanization by spurring innovationto improve services, create jobs, and enhance livability forfuture generations.