We are at the dawn of a mobility revolution, where autonomous vehicles will replace cars controlled by humans. We can imagine this developing along two possible divergent paths with very different implications for cities. Will we create an ownership society with private, driverless cars? Or a world of lightweight, shared social mobility robots available to all? In this CityScope project, extreme versions of these two futures are presented. In one, streets are dominated by machines and density leads to congestion and anxiety. The other is a more vibrant city where humans recapture streets and density increases equity and creative interactions. We propose that new mobility systems must be explored to meet the profound challenges of the future and to enable dynamic and evolving places that respond to the complexities of life.