## 4 Discussion  
The integration of multi-source archival data for 3D reconstruction of non-existent historical buildings presents both unique opportunities and significant challenges. This study demonstrates how a comprehensive and well-structured approach can provide an accurate digital recreation of historical structures, offering new insights into heritage preservation and virtual tourism [5, 6]. One of the primary advantages of integrating multi-source archival data, including photographs, sketches, architectural plans, and written descriptions, is the ability to produce detailed and contextually accurate 3D reconstructions. By cross-referencing different types of documents, discrepancies can be minimized, and a more holistic understanding of the building's original appearance can be achieved. Moreover, the use of advanced digital tools facilitates the preservation of cultural heritage, allowing future generations to experience architectural marvels that are otherwise lost. This has profound implications for both educational purposes and the enhancement of virtual heritage experiences, broadening accessibility and engagement with history [5]. The multi-source approach also enables the reconstruction of architectural elements that might not be well documented in a single source [45]. For example, a written description might provide critical measurements that are not available in photographs, while artistic renderings could capture ornamental details lost in technical plans. Such synergy enhances the robustness and fidelity of the reconstruction process. Despite these advantages, several challenges persist. First and foremost, the quality and completeness of archival materials can significantly impact the accuracy of the 3D models. Many historical records have deteriorated over time, and gaps in documentation are common, requiring researchers to make interpretative decisions. These decisions can introduce subjectivity and potential bias into the reconstructions. Furthermore, discrepancies between different sources are not uncommon; reconciling these requires careful consideration and often necessitates compromises that may not fully satisfy all historical accounts [9, 12]. In this analysis, all archival data considered in the 3D modeling of build  
Figure 30: The 3D models of the buildings at **(a)**\(1\) **T**omackie Street, **(b)**\(3\) **T**omackie Street, and (c)**\(5\) **T**omackie Street. ings were derived from the pre-war period. During those years, the buildings were not reconstructed and their facades remained unchanged. Another significant challenge lies in the computational requirements of processing large and diverse data sets. The alignment and integration of varied source materials into a cohesive model can be both time-consuming and technically complex. Additionally, the requirement for specialized software and expertise limits the accessibility of this methodology, particularly for smaller institutions with limited resources. The main limitation of the proposed methods is the significant time consumption associated both with data acquisition (searching archives, reviewing online sources, and historical collections) and with data processing and the development of the final building model. The time required to implement the proposed method (from field measurements to the development of a 3D model) depends on the size of the object and on the kind of input data.