Our cities are often characterised by a complex, ungrammatical articulation of spaces, volumes, intended uses, and values. The residual green urban areas are representative of a low level or absence of order, but above all, of functions and values. The study proposes a new methodological and operational approach to the rehabilitation of green residual urban areas, participatory type that can generate a new order between values, functions and actors, to mediate private and public needs, to promote new forms of responsibility and thus to implement some of the priority objectives set out in the 2030 Agenda. The operational tools supporting the approach are the Contingent Valuation Method (CVM), public and private partnership (PPP) and crowdfunding. This approach supported the selection of the project and the creation of a budget with public and private funding to support the participatory rehabilitation of a residual green urban area in the municipality of Acireale. The amount of funding identified largely covers rehabilitation costs. The issue of the quality and quantity of urban greenery is crucial for the sustainability and resilience of cities to climate change. Rehabilitation of remaining urban green areas is an opportunity to meet the new needs of green areas, supporting communities in this new challenge.