There has been no lack of architectural responses to the threat of rising tides, especially in the metropolitan cities of the Global North; in fact, what might be called ‘climate megastructures’ have become something of an entire genre of architectural proposal, both real and fictional. Going beyond more prosaic calls for the sustainability of individual buildings, climate megastructures operate at the scale of neighborhoods, cities or regions. Some are imminently buildable, based on contemporary technologies and knowledges up to the task of mitigating sea level rise and the increasing frequency of storms associated with it. Others are far more speculative and cleave to a faith similar to that found in climate geoengineering — the belief that humanity can, someday, figure out a technological magic bullet that can stop or even reverse the worst of climate change. Large, infrastructural-scale thinking is a first step in the right direction towards coping with a problem as daunting and inevitable as sea level rise. But too often, both of these categories of climate megastructure share a common, deeply flawed assumption: that architecture can, and should, be deployed to rescue the urban status quo in the face of existential threat. “Green” megastructures that dutifully fulfill their role as an economic investment first — or just ignore their own place in a global real estate industry that ensures the consequences of climate change will be unevenly felt — might be “thinking big,” but fail to think systemically. When architecture proposes to save the flooding cities of the world, who or what exactly is it trying to save?