## 1 Introduction  
In the recent decade, 3-D technologies have been widely used in archeology in order to protect historical and cultural heritage, aiming at creation of 3D models of various archaeological sites. The purpose of 3D models is not only to visualize and popularize scientific knowledge but also to preserve and present scientific information. Methodologically, two main lines can be noted: fixing the modern condition of archaeological objects, site or exhibits and reconstructing their original appearance. For the first line, various methods, for example, photogrammetry [1, 2, 3, 4, 5, 6, 7], laser scanning (TLS) [8, 9], LiDAR technology [10], etc., are applied when it is necessary to determine and investigate the present 3-D geometry of an object, i.e., to obtain a 3-D image of the current state of an archaeological site or exhibit with the aim of creating a virtual exhibition. The second line comprises the creation of 3-D geometry of a lost or destroyed site based on materials from archaeological research, historical descriptions and analysis of surviving analogies [11, 12, 13, 14, 15, 16, 17, 18]. As the output of both described methods, 3-D models used to create virtual reality (VR) in scientific, educational and exhibition activities can be obtained [8, 9, 19]. This is consistent with the provisions of the London Charter [20]  
The aims, methods and dissemination plans of computer-based visualization should reflect consideration of how such work can enhance access to cultural heritage that is otherwise inaccessible due to health and safety, disability, economic, political or environmental reasons or because the object of the visualization is lost, endangered, dispersed or has been destroyed, restored or reconstructed. The present study is an example of the second line with the purpose not only to demonstrate the historical site but also to carry out historical research, which means studying narrative sources, archival data, doing exploration, reading the literature on similar fortresses and types of military camps [10; 11; 12; 13; 14; 15; 16; 17; 18] and kanabs and analyzing reconstruction paleolandscape [21]. The present work required in-depth analysis and support of each statement in accordance with the \"principle of transparency\" to eliminate or minimize speculative conclusions and decisions. The Pitiunt Fortress, situated in the modern city of Pitsunda (Abkhazia), along with the other fortifications of the Roman Empire such as Apsar, Phasis and Sebastopolis, is one of the most significant classical monuments of the Roman expansion on the Eastern Black Sea coast. The state of modern preservation compares to that of the Apsar fortress which underwent several periods of reconstruction and was maintained by the Ottoman Empire until 1878, resulting in its present perfect condition. However, the Pitiunt fortress, unlike Apsar, lost its significance after the 6 th century AD, when it was abandoned by the garrison, and since then has not been restored. In this regard, at present, the fortress can be described as extended remnants of walls and foundations of internal structures, overgrown with subtropical vegetation, which conceal the greatness of the site (Figure 1). Meanwhile, the Pitiunt fortress figured prominently in the chain of Roman fortifications in the Eastern Black Sea region in the first centuries AD, and therefore, its archaeological study is of great interest for the historical and archeological science. A 3D reconstruction of the exterior of the fortress during its prosperity, 4 th century AD, will highlight the significance of the fortress at that time.