The scientific evidence and consensus of international scientists on human-induced global warming is no longer deniable. There are rising public expectations about environmental issues, and with the right leadership, we are in a position to take huge steps forward. Most urban designers would generally agree that cities and urbanised areas in the developed world need to be our focus, as it will be here, that most energy is consumed and most waste produced. One major aim is to facilitate the revitalisation of pedestrian-friendly city centres that reduce vehicular dependency, and implement the principles of 'green urbanism'. Sustainability aims are most effectively pursued when clear principles of sustainable urban development are established. A 'mixed-use, compact city model' promises the optimum use of space and a new city's land use pattern. Two case studies based on the application of sustainable urban design principles in the Australian city of Newcastle are the 'City Campus' and 'PortCity' projects and they evaluate these scenarios. The 'City Campus' has a focus on regeneration of the city centre as a key principle of the sustainable city; the 'PortCity' showcases a focus on transformation and redevelopment of the harbour area as a model for sustainable expansion of the city. Both projects are based on a balanced approach, high in ambition regarding urban ecology and the aim to run the city centre on renewable energy.