## 1 Introduction
The mine is now abandoned, providing the opportunity to characterize it as a full-fledged, open-air geological museum, suitable for the study and recording of volcanic products of the largest eruption occurred in Santorini in the last 10,000 years (Minoan eruption), and one of the largest of its kind on Earth [13; 14; 15; 16]. Every year, students from all over the world use this site for learning, due to the presence of the famous Late Bronze Age (LBA)-section located in the western part (Figure 2c) of the mine, where almost all volcanic phases of the Minoan eruption are exposed. The mine is characterized by steep cliffs up to 15 m in height, inaccessible to classical fieldwork and data collection; and is subject to almost continuous rock falls and debris flows that make approaching the mine faces extremely dangerous. Figure 1: Overall conceptual workflow used in the present work; each box is related to a relevant part of the manuscript (VR: Virtual Reality, UAN: Unmanned Aerial Vehicle, IVR: Immersive Virtual Reality, GIS: Geographic Information System, DSM: Digital Surface Model). In addition to classical field surveys (e.g., [20; 21]), volcanic areas have been studied by high-resolution, remotely captured images, Orthomosaics and Digital Surface Models (DSMs), especially using unmanned aerial systems (UASs), also known as drone or Unmanned Aerial Vehicles (UAVs), which have high resolution imaging capabilities and an ability to map steep to vertical slopes (e.g., [22; 23; 24; 25; 26; 27]). Following the drone survey, UAV-captured images are combined with Structure from Motion (SfM) photogrammetry techniques [28; 29; 30; 31] to derive the ortho-mosaic imagery and digital surface model. Data collection and GIS analysis using these high-resolution models enable significant advances in research activity, while allowing user interactivity for mapping and measurement purposes that is still crucial for geologists. The use of IVR for survey and data collection in volcanic areas allows the user to walk within an area and around outcrops, switch to flying mode to map vertical cliffs, and, more importantly, map features and take measurements in the same way as when working in the field. The VR scenario we used is based on the creation of high-resolution, scientifically correct (i.e., referenced and scaled) and real-world 3D Digital Outcrop Model (DOM), as firstly suggested by [PERSON] et al., (2018) [32] and successively improved by [PERSON] et al., (2019) [33]. In both cases, UAV-based Structure from Motion photogrammetry techniques are used to build the real-world based VR scenario. In addition to the above, we demonstrate the importance of collecting data in IVR and further elaborate their usage in a GIS environment. Virtual reality (VR) has been integrated with GIS for some time within the academic and industrial communities over the last 30 years. A variety of spatial analysis software programs are available for handling a wide range of spatial problems, beginning with approaches for describing spatial objects with quite complex analyses and  
Figure 2: **(a)** Location of the Metaxa Mine within the Santorini Volcanic complex (modified from [17; 18]). **(b)** Satellite view of the Metaxa Mine area, where the part that has been surveyed in the present work is highlighted by the black box (modified from [19]). **(c)** Panoramic field-view of the famous Late Bronze Age (LBA)-section, in the western part of the area (modified from [19]). 3D visualization. GIS has proven to be the most sophisticated system that operates with the largest scope of objects (spatial and semantic) and relationships and provide means to analyze them while at the same time being able to intergrade data from many different resources (e.g., [34; 35]). Specifically, the current research in 3D GIS is mostly focused on topological models, frameworks for representing spatial relationships and 3D visualization (e.g., [36; 37; 38; 39]). Another significant area of 3D GIS research is devoted to Web applications.