This thesis investigates a specific, hypothetical climatic scenario: the collapse of the Gulf Stream. Though recent studies have raised concerns over its increasing likelihood, the topic remains largely unexplored architecturally. Such an event would drastically alter Porto’s climate — with a sharp temperature drop of 10–15°C, drier summers, and heightened flood risk due to sea level rise. Situated on the western coast of Europe, Porto’s climate is strongly shaped by the Gulf Stream. As a city shaped by its river and coastline, Porto would face both physical and cultural transformations in its absence.

The thesis proposes a design response that embraces these future conditions by “letting the water in.” Rather than resisting the climate, the design introduces a new edge to the city that is permeable, adaptable, and shaped over time by the presence of water — revitalizing Porto’s connection to the Douro River. Materials are selected not only for resilience but also for their capacity to weather and erode, allowing the river to sculpt and transform the architecture over time. Water is invited into certain interior spaces to alter acoustics, programme, and atmosphere — creating a spatial narrative that reflects the city’s cultural adaptation.

Inspiration is drawn from Porto’s medieval city wall — once a line of defence against people — reimagined for the 21st century to negotiate a new adversary: climate. The thesis explores the themes of architectural resilience, adaptation, and mitigation to offer a hopeful response to climate change — showing that cities can coexist with the climate.