This document discusses how smart cities and digital technologies can improve urban sustainability and resilience. It provides background on aging infrastructure in cities and increasing pressures from population growth, climate change, and other factors. The concept of a smart city is introduced, drawing inspiration from human intelligence with layers of sensing, analysis, and control. Digital technologies like smartphones, social media, video surveillance, and high-capacity computing enable new data sources for building digital models and monitoring cities. A case study is described of the SunRise Smart City Demonstrator project in France, which used sensors and data analytics to improve management of urban water, sewer, and heating systems. The document argues that smart cities combined with collective intelligence can help address sustainability and resilience challenges