Cities are humanity’s greatest invention and its most dangerous gamble. They are hubs of wealth, creativity, and opportunity, but they are also the epicenters of environmental breakdown, fragility, and inequality. This paradox is the reality of the twenty-first century and is not only rhetorical. Cities produce almost 70% of the world’s carbon emissions and use more than three-quarters of the world’s energy [1, 2]. They consume materials, water, and land at previously unheard-of speeds. However, cities are also the places where creativity, culture, and group effort are most strongly expressed, and where the answers to social disintegration and climate change must be developed.