Book excerpt: Addresses the multi-disciplinary aspects of urban planning, a result of the increasing size of cities, the amount of resources and services required and the complexity of modern society. Innovative tools are required for identifying the high complexity of contemporary cities. It is necessary to provide a more scientific approach to urban studies, inspired by Prigogine's theories of dissipative structures, and to highlight relations between different systems and between systems and the environment. The challenge of placing sustainable contemporary cities lies in considering the dynamics of urban systems, exchange of energy and matter and the function and maintenance of ordered structures directly or indirectly supplied and maintained by natural systems. The task of researchers, aware of the complexity of the contemporary city, is to increase the capacity to manage human activities pursuing welfare and prosperity in sustainable cities.