This report shows an example of virtual modelization applied to a heritage construction, the walls of the city of Hondarribia. Therefore, it is not a model recreating a building upon hypothetical data obtained from archaeological remains but a true representation of the walls, as we know them today. To accomplish the model, first of all, it is necessary to create a three dimensional geometric model using surveying techniques in order to guarantee the metric accuracy expected in order to meet further cartographic and restorational needs. After bringing together the necessary documentation, a mesh-covered model is obtained which is prepared to be draped with real high-resolution photographic textures, which in turn must be geometrically corrected to eliminate the distortion accentuated by perspective and consequently position the pixels as close as possible to their real place. The process we have just described had been tested in previous projects and yielded satisfactory results. However, more extensive projects as the one in Hondarribia become almost unfeasible due to the huge amount of information involved. The following paragraphs will show the tips used to solve this handicap.