The challenges of designing and planning the twenty-first-century city are shared by nations all around the world. Increasing urbanization and densification in global cities raise the social, economic and environmental pressures on the people that live in them now, and this is set to only increase for future populations. Children and young people, from birth to 18 years of age, represent a vulnerable and marginalized segment of the urban population, susceptible to having their needs and considerations overlooked by the prevailing adult agendas and priorities. What might cities look like in 50 years if the children and young people of today were active participants in imagining the built environments of their future?