This year, for the first time in human history, there are more people worldwide over age 65 than under five. Cities are on the front lines of this demographic shift. In the United States, a record 20 percent of the population live with multiple generations under one roof. How will city leaders respond to these unprecedented demographic and urban shifts? As urban populations grow older and more diverse, age-forward designs and advanced technologies can drive a new blueprint for 21st-century development. By reimagining community models and investing in multigenerational solutions, cities of the future will not only adapt to a new age demography, but thrive from it.