## 1 Introduction
### General Strategies Adopted and the Added Value of the Project  
#### 1.4.1 Role and Use of Virtual Reconstructions, Levels of Representation, Technological Choices  
The use of virtual reconstruction has a central role in the e-Archeo project [34]. In order to favour the understanding of the archaeological space and of the chronological evolution of the site, three kinds of visualisation and storytelling have been implemented, both in the case of holistic vision (territorial scale) and of specific buildings or contexts (monographic scale):  
1. Today's \"archaeological landscape\" associated with descriptive and narrative contents;
2. \"potential ancient landscape\", through virtual reconstructions associated with descriptive and narrative contents;
3. \"interpreted landscape\", through the application of symbolic colours to the various elements of the virtual reconstruction, corresponding to different reliability levels; these latter are also connected to the interpretative sources and processes that have supported the reconstruction. This visualisation is associated with the scientific back end.  
These visualisations may consist of:  
* 360\({}^{\circ}\), still or animated, interactive rendering (equirectangular projection);
* Simple VR scenes, in case of visualization of museum objects, accessible also on common smartphones.  
The metaphor of MR is managed by a web app through the visitors' personal mobile devices.  
The recommended solutions for scenario visualisation are 360\({}^{\circ}\) panoramic views. This choice breaks down problems of technological compatibility, computational overhead, the complexity of interfaces, user disorientation and consequently the loss of motivation.  
Therefore, for each context, these three levels are rendered from camera positions perfectly overlapping so that the user can switch among them without becoming disoriented: such alternation allows them to better compare and understand the space, through the perception and critical elaboration of redundancies and differences [35].  
Moreover, the integration of the three representations increases the accessibility of the archaeological site (and therefore the usefulness of the applications) in case users cannot perform a real visit experience.  
Rendering in a realistic graphic style is associated with the narration or description of the environment; rendering in a symbolic graphic style is associated with the scientific back end and interpretative sources. Descriptions and narrations are available both in audio and written formats to enhance accessibility.  
Besides the general exploration of the whole environment, even a richer interactive experience is possible thanks to the integration of a perfectly overlapping semantic map [36] on the rendering. This semantic map defines, more in detail, meaningful interactive elements in the scenario that can be identified as transparent flashing colours and can be queried, in order to go deeper into the contents (Figure 2).  
Virtual reconstructions have offered the opportunity not only to simulate ancient urban and architectural contexts but also to contextualize objects coming from the site and today preserved inside museums (Figure 3).  
Figure 2: Virtual reconstruction of the Tomb of Reliefs in Cerveteri, 360\({}^{\circ}\) interactive image, with semantic map applied in order to show the interactive elements that can be deepened.