The widespread adoption of smartphones and other sensor-capable devices and the availability of infrastructure capable of storing and sharing sensor information have been the main enablers for the intriguing and ambitious concept of Reality Mining. Reality mining is concerned with the collection and analysis of sensed data pertaining to different aspects of human social behavior, allowing to observe the societal dynamics and predict what individuals will do next, model the behavior of large organizations, detect trends, spot emerging phenomena and events, mine public opinion, etc. The concept of reality mining is even more intriguing when applied in the context of urban space, since user-generated content can be analyzed to reveal the citizens' perspective on various aspects of the city reality. In this paper, after elaborating on the concept of reality mining in urban space, we present three cases where user-generated content is employed to discover the citizens' perspective about: a) the city attractions, b) the city issues/problems, and c) major events in the city.