Cities around the world are increasingly developing city-wide lifelong learning strategies to promote individual and civic adaptation to major economic, technological, and environmental challenges. Such initiatives, however, have not yet received commensurate research attention from education researchers and it is not yet clear that we have the theoretical or methodological tools to research the complexity of learning at a city scale. This paper attempts to outline one approach that might respond to this challenge by drawing on the concept of 'lively infrastructure' from urban studies. Based on 11 months of detailed ethnographic fieldwork in the city of Bristol, the paper draws on this concept to trace how learning infrastructures are produced, accessed, and reshaped by individuals and serve to provision particular forms of learning in the city. In so doing, the paper argues that learning infrastructures need to be understood as discursive, material, and affective; as deeply interconnected with other city infrastructures, particularly childcare and transport; and as capable of morphing to create both radical new forms of learning activity as well as consolidating existing practices of exclusion and inequality.