This course provides an introduction for student to explore ‘urban sustainability.’ How do we define and achieve sustainable cities? How can we make Hong Kong as a sustainable city? We discuss problems of energy supply and costs, food supply, water management, infrastructure and buildings, and social relations (justice) and environmental issues such as climate change. Through discovery-enriched approaches, we examine and discover some real-world case studies from cities and towns in Asia and elsewhere to illustrate both problems and solutions. The course includes a variety of learning activities such as debate, discussion, presentation, guest talks and a field study to seek theoretical and practical explanation and solutions for sustainable cities in the 21st Century.