Soft City Culture and Technology: The Betaville Project discusses the complete cycle of conception, development, and deployment of the Betaville platform. Betaville is a massively participatory online environment for distributed 3D design and development of proposals for changes to the built environment an experimental integration of art, design, and software development for the public realm. Through a detailed account of Betaville from a Big Crazy Idea to a working "deep social medium", the author examines the current conditions of performance and accessibility of hardware, software, networks, and skills that can be brought together into a new form of open public design and deliberation space, for and spanning and integrating the disparate spheres of art, architecture, social media, and engineering. Betaville is an ambitious enterprise, of building compelling and constructive working relationships in situations where roles and disciplinary boundaries must be as agile as the development process of the software itself. Through a considered account and analysis of the interdependencies between Betaville's project design, development methods, and deployment, the reader can gain a deeper understanding of the potential socio-technical forms of New Soft Cities: blended virtual-physical worlds, whose "public works" must ultimately serve and succeed as massively collaborative works of art and infrastructure.