This thesis project presents a comparative analysis of the city of Coimbra (Portugal), modelled according at its current and present physiognomy (2021) to a compact version of itself; aiming at identifying an urban planning tool able to emerge as one of the possible ways to achieve a sustainable development of the city. The tool chosen for the interpretation and numerical comparison of the two models was identified in the accessibility index, a position-based indicator, calculated through a digitization of the built and inhabited areas in a GIS environment. The results, summarized in indexed maps and tables with weighted average distances per inhabitants to facilities, show how the compact city reduces the average distances between inhabitants and facilities by 70%, with peaks (on maximum distances) of 81%.