In this paper we present our vision on the Sociable Smart City. In our view cities are the people that inhabit them, their memories, stories, concerns and the culture that develops through their social interactions. The application of urban computing has a significant social and cultural impact on the city and on city life. Attempting to realise our vision, we designed and deployed CLIO, an urban computing system aiming to allow people to interact with the collective city memory. Our findings revealed that a system that exploits city infrastructure and both people's and artificial intelligence in order to empower and engage them in social activities may enhance citizen participation and sense of belonging as well as it may enable urban social interactions.