Book excerpt: Planners internationally have employed green belts to contain the explosive sprawl of cities as varied as Tokyo, Vienna and Melbourne during the twentieth century. As yet, no collection has gathered these experiences together to consider their contribution to planning. Juxtaposing examples of green belt implementation worldwide, this book adds to understanding of how green belts can be effected in theory and how practitioners have adapted them in practice. The book provides a typology of green belt implementation and reform, enabling planners to grasp why these policies are employed and whether they are relevant to twenty-first century planning.