<p>The possible effects of surface topography on the seismic ground motion are addressed in some seismic codes through the use of suitable proxies. In the European seismic code and in its Italian implementation, expected amplification factors are associated to a small set of 2D schematic morphological configurations. These proxies have been assessed based on numerical simulations in the assumption that the respective configurations are representative to 2D morphologies. To test the feasibility of these estimates in a real morphological context, the city of Siena (central Italy) has been considered as test site due to a nearly homogeneous seismo-stratigraphical configuration corresponding to a relatively complex morphology. A multi-step approach has been carried out on purpose, which integrates GIS and DEM-based spatial methods, and numerical modeling to check the reliability of code proxies by preliminarily identifying the real morphologies best fitting the simplified profiles in the norm and corresponding to a 2D morphology. Numerical modelling performed by considering a set of representative profiles indicates that amplification values provided by the norm perform relatively well in the range of periods of structures if discrepances below 0.1 are considered as acceptable. On the other hand, the fact that the proxies are expected to be applied in the case of 2D morphologies significantly reduces the number of cases where these proxies can be applied and increases the number of morphological situations requires advanced numerical modelling. Anyway, this study also puts in evidence that any evaluation of effectiveness of the topographic amplification factors provided by the norm relies on a clearer definition of its aims in terms of expected accuracy and application domain.</p>