This chapter is about the challenges and opportunities that urban centers face. Urban centers are expanding beyond traditional urban boundaries in a process called urban sprawl, which consumes a lot of land. While there are certainly megacities with populations of more than 10 million, a lot of population growth will occur in small and medium cities. There are even a few shrinking cities. Key challenges ahead include increased resources needed for growing, affluent populations. Local governments need to address land consumption and management in an active way moving forward. An enormous and sustainable investment in infrastructure is needed; urban areas can also benefit from ecosystem services. Using the example of urban heat waves, we explore opportunities to combine the built environment with the living environment. The majority of people living in cities will be below the age of 20, so urban solutions must engage young people.