This paper reports on research in the area of 'Green Urbanism' and new models for urban growth and neighbourhoods, as cities need to transform from a fossil-based model to a model based on sustainable energy sources. Among the most significant environmental challenges of our time are excessive fossil fuel dependency and the growing demand for energy - all likely to be major challenges for urbanism in the 21st century. In this context, urban design and the fundamental principles of how to shape our cities has barely featured in the greenhouse debate. Much of the debate in related areas has so far circled around ideas about active technology for 'eco-buildings'. This is surprising, since almost half the energy consumed is used in cities and urban built-up areas, and given that avoiding mistakes in urban design at early stages could genuinely lead to more sustainable cities and less greenhouse gas emission. several big cities in the developed world have now started initiatives focussed on energy transformation in urban areas to reduce their dependency on oil and gas sources. The paper deals with cross-cutting issues in architecture and urban design and addresses the question of how we can best cohesively integrate all aspect of energy systems, transport systems, waste and water management, passive and active strategies, natural ventilation and so on, into comtemporary urban design and improved environmental performance of our cities. This text reflects upon practical strategies focused on increasing sustainability beyond and within the scope of individual buildings and provides a context for a general discours about the regeneration of the city centre, its transformation to a sustainable model, and discusses how urbanism is affected (and can be expected to be even more affected in the future) by the paradigms of ecology. Research in sustainable urban design recommends increased harnessing of energies manifested in the existing fabrics, through the adaptive re-use of former industrial (brownfield) sites and the upgrade of the existing building stock. Recent examples for the application of such urban design principles are the two proposals for the Australian city of Newcastle: the 'City Campus" and 'Port City' projects. These case studies illustrate, it is less environmentally damaging to stimulate growth within the established city centre rather than sprawling into new, formerly un-built areas.