This paper investigates the historical trajectory of Quinta Nova, more widely recognized as Quinta dos Ingleses (QI), located in Cascais, and examines the citizen-led movement advocating for its preservation as a public green park. The case is situated within broader debates on sustainable urban development and the contestation of dominant urbanization paradigms. Dating back to the eighteenth century, Quinta dos Ingleses constitutes a site of substantial cultural and ecological significance. Yet, its continued existence is imperiled by large-scale urbanization projects that privilege intensive development over heritage and environmental conservation. The site thus occupies a dual position: it functions simultaneously as a historical landmark and as an ecological enclave within an increasingly urbanized coastal territory. This study further analyses the mobilization strategies of the grassroots initiative SOS Quinta dos Ingleses, interrogating the challenges it encounters in countering the interests of powerful real-estate actors and local government policies that promote high-density development models. Through this analysis, the paper foregrounds the discursive struggles over the value and function of urban green spaces, particularly within the tension between high-density growth and more ecologically attuned planning frameworks. In evaluating the proposal to transform Quinta dos Ingleses into a public park, the research considers the project’s potential to serve as a balanced alternative that reconciles urban growth with the protection of cultural heritage and ecological assets. Particular emphasis is placed on the contributions of such an initiative to environmental sustainability, the enhancement of urban quality of life, the strengthening of social cohesion, and the bolstering of resilience to climate change. Ultimately, this case study underscores the significance of civic engagement in advancing sustainable urban futures. It demonstrates the capacity of local movements to challenge entrenched development logics and calls for the systematic integration of natural and historical preservation into urban planning frameworks at both local and global scales.

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