## 1 Introduction
### State of the Art on XR and Accessibility for Cultural Heritage
The user can observe such animations in 360\({}^{\circ}\) using the sensors on the device (compass, accelerometer and gyroscope). Therefore, if such an experience is activated in the same real place to which the scenario refers, a collimation impression will be possible: the user, who has reached the observation point, will be asked to orient himself according to specific coordinates and the exploration in MR will be truthful, thanks to the orientation sensor technology. This solution, although technologically less pioneering, is at present more robust, generally of better quality and easy and immediate in use. It is also compatible with the most common user devices (smartphones, tablets, cardboards, up to immersive head-mounted displays, etc.). The advantage of offline tracking with device orientation is that the experience can also be enjoyed remotely, just as with VR, without necessarily being on-site. This distinction between tracking features in real time or through offline calculation with device orientation is therefore fundamental and determines distinct choices in the design of the user experience and the conception of the entire application. VR focuses on enhancing human presence and interaction with a computer-generated environment without any connection to the real world. Within VR, there are more or less immersive experiences and different types of interaction: from fruition via smartphone, tablet and desktop devices [18] to semi-immersive installations with gesture-based interaction [19; 20]; from immersive projections [21] to HDM devices [22]. When choosing the most appropriate technology for a multimedia enhancement project, it is necessary to establish the type of use aimed at, bearing in mind the limitations of the various resources. AR in archaeology, for instance, can be effectively applied to show a disappeared context virtually reconstructed in situ. Therefore, it has the limitation of being extremely site-specific and not being able to provide an adequate experience through remote usage, limiting the accessibility of content only to those who can physically reach the site or the museum. In VR, an important discriminator is the rendering calculation of 3D scenes. Real-time rendering (RTR) allows greater freedom of interaction and movement within virtual environments. However, it has the technological limitation of tying fruition to specific contexts where high-cost fixed installations are present since the rendering calculation must be performed by high-performance devices in order to guarantee a high-quality graphic rendering. On the contrary, applications built through pre-rendered content, such as 360\({}^{\circ}\) panoramas, also allow their fruition through mobile devices, albeit with the navigation limited to zoom and rotation commands only. This second case, which concerns all applications conceived as virtual tours, also makes it possible to bypass the criticality of sharing single-user devices for cultural fruition in the COVID-19 era. In the e-Archeo project, it was decided not to use tracking technologies for many reasons, although we were aware of the potential they could integrate. After a careful evaluation of the context in which the project was conceived and the leading causes of the decline of technology platforms related to previous valorisation projects, we focused on two main objectives: to reach as many users as possible and to create sustainable usage models for the management by museum institutions to ensure their durability. Although not introducing any technological advancements, the strength of the e-Archeo project lies in its dissemination and long-term sustainability. The challenge was to realise a modern, high-quality enhancement project which could be adapted to different museum contexts while keeping the technological framework as simple as possible.