The (proposed) development of private sector-led, large-scale urban projects on the periphery of many African cities has drawn increased attention to the geographical breadth and potential consequences of the phenomena in recent years. This work demonstrates the speculative nature of many of these projects and their 'world-class city' aspirations, but also how such plans will exacerbate existing problems, including spatial inequality and environmental degradation. This paper, drawing on 50 interviews and extensive fieldwork, examines one such project in northeast Johannesburg, the Modderfontein New City. The paper responds to existing research and their calls for more grounded studies, and argues that given their distinct logics and developmental mechanisms, large-scale masterplanned edge cities can only truly be understood within the context of their place-specific urban landscapes, and that contrary to the prevailing arguments on this type of project, they do not always exist outside of ordinary governance structures. Supporting the (speculative) conclusions in earlier research, we demonstrate how the plans and early building looked to worsen spatial inequality and environmental problems. However, in highlighting how Modderfontein's failure is partly the product of a strong local state unwilling to compromise on their own agenda in the face of elite-driven edge city developments, we argue such large scale projects in Johannesburg face hitherto under-researched disciplining processes that can disrupt or even derail projects.