Aldo Rossi’s work has received a great deal of attention since the mid-1960s. Books, exhibitions, conferences, and articles have established that for Rossi the city was a crucial reference both in the production of his architecture and for overcoming the crisis of rationalism that exploded after World War II. Yet one question has remained open, with critics, historians, and architects offering discordant and inconclusive answers: what relationship did Rossi weave between his architectures and their cities? This article provides an answer to that question, identifying for the first time the origin of that relationship in Italian postwar ambientalismo, which proposed rebuilding the historic city centers with architectures generated by edilizia, the anonymous building fabric that surrounded the project sites. The article discusses the evolution of that relationship, demonstrating how Rossi came to develop, from the beginning of the 1960s, a poetics capable of overcoming ambientalismo, cannibalizing it to operate on the edges of cities, where he replaced the edilizia, with the monument, the project site with the territory, and the mechanical transposition of the characteristics of places with the analogy. This novel analysis of Rossi’s work through a comparison to ambientalismo is not limited to explaining the relationship between his architecture and cities. It also questions the classic interpretation of Rossi’s research by demonstrating how Rossi destroyed the traditional image of the historic city to build a ‘new urban landscape’ that was free of edilizia and consisted solely of lawn and monuments.