Aurélien Delpirou brings a new perspective to the debate initiated by Luis Santos y Ganges. He highlights the fact that urban planning policy alone, even when based on the development of rail infrastructure, does not make for a city. The example of the Italian capital shows that, when it comes to integrated urban development, plans are there only to set the ground rules for a game played by other participants. These plans are confronted with not only the contradictions of sustainable development, but also the inertia of relations between the municipal government and developers.