No contemporary major city is sustainable, with current population and levels of consumption, beyond the fossil fuels which have facilitated what has appropriately been called "high-energy modernity." At present, there appears to be no realistic possibility in any major city of replacing most of the energy from fossil fuels with renewable energy. Even in cities which could get most of their electricity from renewables, there is still a heavy reliance on motorized transport of people, goods, and food into and around the city. There does not appear to be a way to power and reproduce these fleets of vehicles solely with renewable energy, and most cities are not sustainable at their current size and density without them. But cities and regions vary in sustainability depending on local renewable energy sources, hinterland food production, population, extent of urban sprawl, and access to water-borne transportation. This paper identifies the features of more sustainable versus less sustainable cities, with examples from Asia, the Americas, and Europe. Case studies of two cities-Hong Kong and Vancouver, B. C.-are used to illustrate the analysis.