Complexes of urban fortifications are the basis for analyzing historical development of a settlement and developing urban planning documentation. Therefore, in 2014, as part of the publication “Atlas of Ukrainian Historic Towns, Volume1: Lviv”, the authors of the present article published a scheme-reconstruction of the localization of Lviv's historical defensive buildings based on a modern topographic basis. The format of the Atlas did not provide for a full justification of the work done. Hence, the purpose of the present article is to reveal the methodology of the tracing of Lviv fortifications on a modern topographic basis; to substantiate the received results on the localization of fortifications and to determine their evolution. Based on the analysis of the works of predecessors, bibliographic, cartographic, and iconographic sources, three separate historical complexes of Lviv fortifications are identified, and the evolution of the complex of fortifications of the 14th - 17th centuries is highlighted. As a result of combining the drawings of the first three lines of fortifications worked out by J. Witwicki and our results of tracing the fortifications, we have found the high accuracy of J. Witwicki's work. Based on the analysis of sources and archaeological research, we have clarified information in a number of flanking elements and in certain directions of the three lines of fortifications in Lviv. In order to supplement this work with the results of the work of a wide range of scholars, obtained during the twentieth and early twenty-first centuries, we have conducted a pre-project study, the results of which are embodied in the differentiated designation of lost, preserved, and archaeologically recovered fortifications of the 14th and 17th centuries on a modern topographic basis at the scale of 1:2000. As a result of tracing the bastion fortifications of the suburbs, the remains of fortifications from the projects of F. Getkant (1635) and J. Behrens (1678-1682) have been found in the topography and planning structure of the city, as illustrated in the reconstruction schemes.