Sustainable cities are central to achieving all 17 Sustainable Development Goals (SDG). By 2050 cities will contain approximately 70% of the world's population and produce 85 per cent of global economic output. Policy and investment decisions made today will have a deep and long-lasting impact, based on the concentration of people and economic activities, and the long-term nature of urban systems and infrastructure.Urban development should proceed in a well-planned, integrated, and inclusive manner, with city governments working together with businesses, civil society organizations, academia, and individuals, and with national governments, as well as the authorities in neighbouring urban towns and rural areas, and peer cities around the world. A robust “science of cities” can give urban policymakers around the world access to a body of knowledge and good practices.Urban decision makers should take the central tenet of the 2030 Agenda to heart and ensure that no one is left behind in their cities and towns. That means prioritizing pro-poor development and access to decent jobs; high-quality public services, health care and education; sustainable transport; and safe and attractive public spaces for all, regardless of gender, age, ability, and ethnicity.Governments, businesses, civil society organizations and individuals can use a range of policy, economic and communications tools to promote sustainable consumption and production patterns in cities, encourage densified habitat and decouple growth from environmental degradation. Innovative governments, a committed private sector and an active citizenry can overcome inequalities and create livable cities in both developing and developed countries. livable cities offer high-quality services and increase “naturbanity”, a close connection between people and nature, to enhance human health and well-being, protect biodiversity, and strengthen climate resilience, which is particularly important for vulnerable populations in coastal cities and those in informal settlements.