Urban Sprawl, and the fragmentation of the territory associated with it, are factors degrading the peri-urban areas in many European cities. The aim of this research is to investigate the role that Green Infrastructure (GI) and Nature-Based Solutions (NBS) can have in redefining peri-urban areas, relating urban and rural landscapes. The case study focuses on the Southern Milan periphery, at the rural-urban transition fringe; the transformation pressures, tendencies, and local activities are approached, and the main problems are juxtaposed to the potentialities, defining simultaneously the site’s vulnerability and latent resilience. The elaboration of a research-by-design approach focuses on the refurbishment and interconnection of disused open spaces and abandoned buildings: converting them in favor of a GI and NBS network, through a perspective of Ecosystem Services (ES) enhancement, but also encompassing cultural heritage and multicultural aspects. The overall design demonstrates the possibility of deploying an infiltration strategy, of the rural landscape into the urban fringe. The objective is to articulate a multiscalar methodology and give insights on how a GI network can rebalance urban-rural transitioning spaces and enhance ES, improving the quality of marginal spaces both in environmental and socio-cultural terms.