The continued use of existing structures is of great importance because the built environment is a huge economic and political asset, growing larger every year. The assessment of existing structures is now a major engineering task. The structural engineer is increasingly called upon to devise ways for extending the life of structures whilst observing tight cost constraints. Historical immovables which are also existing structures should be assessed elaboratively in order to preserve cultural heritage and repair historical structures. In this study, the steps carried out for generation of 3D CityGML model for a part of (North tower) the Seddulbahir fortress which is in need of urgent renovation due to specific factors (severe weather conditions, vandalism, etc.) that will be used as a base model for restoration and renovation projects and as archive data for the documentation of the fortress will be explained in detail.