The ground plan matters. It matters not only for the fundamental characteristics of buildings, as already discussed, but also for social fabrics, influencing key aspects of people’s lives. The book aims to reveal a consistent cumulative effect of street systems, plot patterns and building arrangements on a succession of fundamental urban layers. This means that a ground plan type that positively influences social diversity is likely to have a similar positive effect on economic diversity and environmental sustainability. This argument is explored through five case studies in all five boroughs of New York: Soundview (the Bronx), Bedford (Brooklyn), East Village (Manhattan), Queensbridge (Queens) and St. George (Staten Island). In general, there appears to be a correlation between the combined density of streets, street blocks, plots and buildings (frontage coincidence) and social performance, measured by median income, employment rate, educational attainment and racial integration. Moreover, not only do these indicators tend to improve as physical density increases, but the range of values also shows potential for growth. The ground plan can contribute to a major goal: bringing together and fostering interaction between people of different races, educational backgrounds, jobs and income levels.