The real-time city is now real! The increasing deployment of sensors and hand-held electronics in recent years is opening a new approach to the study of the built environment. Digital technologies are radically changing the way we understand, design, and ultimately live cities. This is having an impact at different scales – from the single building to the scale of the metropolis. On the occasion of the MIT R&D conference, Umberto Fugiglando will address these issues from a critical point of view through projects by the Senseable City Laboratory, a research initiative at MIT. In particular, he will show research advances and use cases of sparse and crowdsourced sensing technologies for addressing issues in air quality measurements, infrastructure monitoring and wastewater sampling.