Cities are where the battle for sustainable development will be won or lost – they contribute 80% of the global GDP, and account for 70% each of global energy consumption and greenhouse gas emissions. With over two-thirds of the global population likely to live in cities by 2060, this is more than a cliché. A clutch of sustainable cities makes a sustainable province; a clutch of sustainable provinces makes a sustainable country, and it follows that several sustainable countries learning and sharing and helping other countries, will make for a sustainable world in the 21st century and further on into the future.