This paper seeks to explore the origins of these inchoate changes and shifts in perception and experience of urban dwelling places and electronic spaces by tracing out their implications for the agenda of sustainable cities.The paper first considers the movement from Netville, the cybercommunity generated among technical experts and scholars associated with the building of the Internet, to Cybercities, the various online communities emerging from ARPA′s seemingly anarchic communications network. It pays particular attention to the ″rules of play″ that governed the construction of the Internet and the kind of egalitarian community of competence that those rules engendered. The analysis explores the import of those ″rules of play″ for ″Emerald City,″ a sustainability game for designing sustainable cities. The last section then shifts from participatory design process as game to an ongoing design project – the Westbahnhof project. This project, demonstrates the relevance of both the ″rules of play″ and the sustainability game in building sustainable cities of the future in an open, democratic, and participatory fashion.