Creating vibrant urban places is a challenging task in urban design due to the intangible feature of urbanity. This paper presents Form Syntax, a design analytical tool that is capable of assisting urbanity making in design practices based on understandings of three essential urban morphological elements and their influences on urbanity. Using the geographical information system (GIS), Form Syntax integrates three methods—Space Syntax, Spacematrix, and Mixed-Use Index—to measure the street-network configuration, building density, and functional mix, respectively. These three components can be quantified and combined to represent urban morphological features, thereby providing a classification of the degree of urbanity. Form Syntax contributes to geodesign by combining quantitative tools with traditional, intuition-based design to achieve a clear visualisation of the degree of urbanity of a place, which can subsequently be used to propose spatial strategies for enhancing vibrant urban places. The Dutch city of Rotterdam is used to illustrate how the tool improves the traditional site analysis, idea evaluation, and proposal evaluation phases of urban design. A GIS add-in has been developed to enhance the appeal of Form Syntax among urban design practitioners.@en