This document discusses the challenges facing cities in the 21st century. It notes that by 2030, 750 metropolises will account for 60% of the world's GDP, and that cities concentrate both economic opportunity and social/environmental vulnerabilities. The document advocates for smart city solutions that leverage new technologies to create resilient, inclusive, and sharing cities. It emphasizes addressing ecological, social, cultural, and economic issues to improve quality of life in an increasingly digital and interconnected world.