This article explores and expands debates on the geographies of social cohesion and encounter, specifically in relation to young people and informal citizenship training. Three questions drive our agenda in this paper. First, how do certain youth spaces get enrolled into wider political discourses, functioning as geographical expressions of government visions to create a political legacy? Second, how are these spaces engineered and operate on-the-ground? Finally, how do young people understand their experiences of such spaces? To address these questions, we use the example of 'National Citizen Service' -a youth programme operating in England and Northern Ireland -to raise critical questions about the wider politics of spaces of informal education and attempts by the state to 'make' citizens and future neighbours. The article examines the rationale for this growing scheme, targeted at 15-17 year olds and designed to foster a 'more cohesive, responsible and engaged society'. Drawing on original fieldwork with key architects, stakeholders and young people, we analyse the narratives that underlie NCS and its expansion -specifically around social cohesion and citizenship education. We explore the idea of 'social mix' as one of NCS' guiding principles and its place as part of state narratives about the 'Big