The consequences of climate change in developing countries are worsening fast: many ecosystems will shortly reach points of irreversible damage, and socio-economic costs will continue to rise. To alleviate the future impacts on populations and economies, policy makers are looking for the spaces where they can make the greatest difference. This report argues that intermediary cities in developing countries are such spaces. Indeed, in the context of fast population growth and urbanisation, these small and medium-sized cities silently play an essential role in the rapid transformation of human settlements, not least by supporting the massive flows of population, goods and services between rural and metropolitan areas. Most of those intermediary cities are still growing: now is therefore the time to influence their dynamics, and thereby the entire design of urbanisation in those regions, in ways that limit the exposure of urban dwellers to climate shocks and avoid carbon lock-in. To that end, based on fresh evidence and policy analysis on the challenges faced by these agglomerations in the context of climate change, the report makes the case for new development approaches to avoid the unsustainable paths followed by too many cities in the recent past.