This dissertation explores the deteriorating relationship between architecture and public space plaguing many Western urban cores as a result of economic, cultural, political and social forces. It investigates the question of how and why ground floor frontages have been transformed, by comparing the urban cores of The Hague (Netherlands) and Detroit (United States) over the past century. Frontage interactivity is defined as the combination of physical transparency, functional permeability and perceptual hospitality, and is mapped in both urban cores over the span of a century in 10 to 25 year intervals. Interactivity is categorized into four tiers, based on fourteen functional frontage types, ranging from highly interactive retail businesses to dwellings and less interactive offices, parking structures and warehouses. Patterns of physical and functional fringe belt formation and urban erosion are found in the maps and statistical analyses. These analyses demonstrate a pattern of fringe interactivity decline, amplified by an acceleration of decline at the level of the street segment – pointing to the contagion of vacancy and inactive land uses. This interactivity erosion is usually followed and amplified by a rapid morphological change, often fueled by large-scale urban renewal interventions – a pattern that is surprisingly similar in both cities. The forces behind frontage transformation are illustrated by separate histories of The Hague and Detroit. The demonstrated forces and patterns of change are integrated into a set of conclusions, finding significant similarities between both case studies. From an economic, social and cultural perspective both cities have faced and still face similar challenges, albeit amplified in Detroit. The relationship between buildings and public space has deteriorated significantly in downtown Detroit as a result of socio-economic decline, amplified by a culture favoring progress over sustaining a collective memory. The Hague’s inner city has benefited from a somewhat finer balance between progress and permanence, often due to fierce public and political debates. The conclusions are followed by a set of recommendations for how to counter frontage deactivation, focusing on the role of economics, diversity, curbing fear and auto-mobility, and critical mass in reshaping the architecture of public life