Context - The development of urban icons has become a popular strategy for municipalities to reach envisioned spillover effects, e.g. by boosting the urban image or by functioning as a catalyst in the regeneration of an urban area. These iconic developments are not rarely associated with high public investments, which often tend to be based on ambiguous assumptions and ill-defined objectives. Problem statement - Despite the high level of academic attention for the phenomenon of urban icons, the current state of research lacks the availability of a comprehensive methodology by which the spillover effects of urban icons can effectively be measured. Therefore, municipalities are yet unable to apply quantitative measurements to justify previous investments or to substantiate future investment decisions with regards to urban icons.This research is focused on the establishment of an impact assessment approach, as it addresses the following main research question: How can the spillover effects of urban icons be effectively measured? Methods - A qualitative strategy has been applied in this research. A literature study and case study have been conducted to establish the impact assessment methodology blueprint, by which the spillover effects of urban icons can be measured. Based on a literature study and focus group meeting with an expert panel, the implementation feasibility of the prescribed methodology has been determined. Findings - An impact assessment methodology blueprint has been designed to comprehensively, quantitatively and longitudinally measure the spillover effects of urban icons at a high spatiotemporal resolution. The blueprint consists of three consecutive steps: (1) The integration of evaluation in the building process cycle, (2) the development of a big data-based project evaluation methodology and (3) the establishment of a data-driven urban planning practice. The results from the measurements can be applied to justify previous investments and to substantiate investment decisions.The implementation feasibility of the prescribed blueprint is potentially obstructed by the methodological implications, consisting of the high required investments and the culture shift in the urban planning practice that the methodology implies. Furthermore, the effectiveness of the methodology may be negatively affected by a limitation of applicable data sources, as a result of issues regarding data reliability, privacy or ethical concerns. Conclusion - In order to effectively measure the spillover effects of urban icons, municipalities should initiate a culture shift towards an approach in which research and urban planning are inseparably linked. Furthermore, municipalities should invest in the establishment of a methodology in which evaluation becomes an integral part of the building process cycle, big data sources are applied to effectively measure the impact of urban icons and a data-driven urban planning practice is established.