In the connected age, the flow of data through cities is becoming a key contributor to global competitiveness. European cities are taking advantage of public funds to experiment with open access to data and to assess the monetization potential for selected sources. Although estimating the full value of data in the public sector is difficult, government studies suggest tens of billions of euros could be realized. Frost & Sullivan believes that the world’s leading cities will combine ICT infrastructure with digital ‘self-knowledge.’ Here, real-time cities are discussed as those that pursue policy goals through the exploitation of public and private data, sensor networks for monitoring, and control and platforms for collaboration in services.