The attacks of September 11, 2001, changed far more than the skyline of New York. They altered the way architects, planners, governments, developers, and citizens understood the relationship between buildings and risk. Architecture had long been concerned with structural safety, fire protection, natural disasters, and human comfort, but after 9/11, another question moved sharply toward the center of architectural thinking: How should cities be designed when buildings and public spaces themselves can become targets? The answer has never been simple. The decades following 9/11 produced stronger buildings, controlled entrances, security barriers, surveillance systems, redesigned public spaces, new approaches to memorial architecture, and a renewed interest in urban resilience. At the same time, these measures introduced a difficult contradiction. The safer a city tries to become, the more it can begin to resemble a city designed around fear. The influence of 9/11 therefore cannot be reduced to the architecture of the rebuilt World Trade Center. It represents a broader transformation in urbanism, in which security became embedded within the physical fabric of cities around the world. From Iconic Towers to Vulnerable Urban Symbols Before 9/11, the skyscraper represented many things: technological achievement, economic power, globalization, corporate identity, and urban ambition. The World Trade Center embodied these ideas particularly strongly. Its Twin Towers were not merely office buildings but internationally recognizable symbols of New York’s economic and political significance. Their destruction demonstrated that architecture could acquire a new vulnerability precisely because of its symbolic power. The skyscraper was no longer understood exclusively as an efficient vertical workplace. It could also function as a highly visible target. This changed the discussion surrounding tall buildings. Architects and engineers increasingly considered issues such as blast resistance, protected structural cores, multiple evacuation routes, emergency communication, fireproofing, refuge areas, and controlled access. Security began influencing decisions that