The social context of mobile work has dissolved the physical dominance of the workstation. The city, once anchored and animated by the clockwork activity of the downtown office, today absorbs this mobile workforce within coffee shops, parks, and public spaces, blurring distinctions between spaces of leisure and spaces of production. As the most visible threshold between the office desk and the city street, the lobby is uniquely positioned to establish social forms of work as a generator of architectural form. By concretizing public/corporate blurring within a highly visible container in the city, A Commons Lobby leverages the social nature of the mobile workforce to reclaim the office as a hub of social activity and a laboratory for new types of work. Lobbies typically serve as a publically occupiable control point, welcoming visitors while restricting their activity, aiming to impress without inviting anyone to stay. It is a spatial type perpetually at odds with itself. The lobby’s potential to transform the office is no more evident than in San Francisco, where the exponential growth of the high-tech industry has led to an internalization (and economic stratification) of the social and commercial activity that once animated downtown streets. As a site, this thesis operates on a new San Francisco live/work district in need of a formal and programmatic counterpoint to the bland anonymity of the typical office. An increasingly mobile workforce places more, not less, importance on the context and urban implications of production. By opening up the lobby as an expanded threshold supporting social, commercial, and corporate program, a new workplace typology emerges to reestablish the office as an urban protagonist.