The design of every aspect of the urban landscape—from streets and sidewalks to green spaces, mass transit, and housing—fundamentally influences the health and safety of the communities who live there. It can affect people's stress levels and determine whether they walk or drive, the quality of the air they breathe, and how free they are from crime. This book provides a compelling look at the new science and art of urban planning, showing how scientists, planners, and citizens can work together to reshape city life in measurably positive ways. It demonstrates how well-designed changes to place can significantly improve the well-being of large groups of people. The book argues that there is a disconnect between those who implement place-based changes, such as planners and developers, and the urban scientists who are now able to rigorously evaluate these changes through testing and experimentation. It covers a broad range of structural interventions, such as building and housing, land and open space, transportation and street environments, and entertainment and recreation centers. Science shows we can enhance people's health and safety by changing neighborhoods block-by-block. The book explains why planners and developers need to recognize the value of scientific testing, and why scientists need to embrace the indispensable know-how of planners and developers. It reveals how these professionals, working together and with urban residents, can create place-based interventions that are simple, affordable, and scalable to entire cities.