Cities are increasingly becoming tech playgrounds. In partnership with civic and government institutions, tech companies are deploying ‘smart’ technologies in the urban environment, in the name of improving the everyday experience of cities. But for playgrounds, there is often little room for those who live and work in cities to experiment and play with these technologies before or after they are deployed. In this chapter, we draw inspiration from exemplary projects and previous work in detailing a pilot participatory smart city project called Beta Blocks, taking place in Boston, Massachusetts, USA. Facilitating participatory imagination with residents for a future Boston, Beta Blocks invites communities to explore and play with smart city technologies through four key components. First, a physical installation exhibited at different locations across the city. Second, community-designed experiments with smart tech in three neighborhoods in the city. Third, a structured exploration program to design these experiments. Fourth, direct engagement with a number of community organizations and tech companies to foster productive relationships during and after the project.