## 4 Discussion and Conclusions  
The mobile application HUSH has been designed by integrating synergically different professionals using a multi-disciplinary approach that has characterized both the research stage and the application framework. Geologists, naturalists, physicists, and computer scientists have worked together in each step. The topic of the project was to realize an advanced mode of fruition of naturalistic (geological, fauna, and vegetation) and artistic sites in the urban area through the fusion of itineraries of interest and access to augmented reality content (AR). The naturalistic value of a site is generally associated with sparsely populated areas, while in urban areas different interests prevail. Naturalistic content therefore represents unexpressed potential, which if appropriately valued in AR could represent a strong precursor of development. With this in mind, the major expected outcomes of HUSH are:  
* To identify in an urban context naturalistic values, starting from the historical center and ending in green areas. * To realize innovative fruition via AR tools of virtually moving in space and time, triggering awareness-raising practices. * To expand the potential for economic development by linking AR content to local businesses (e-advertising). * To integrate society into the processes of scientific research. HUSH guides the user through points of scientific interest in urban areas. The points of interest merge the historical-artistic value of the historic center with its naturalistic values. This is accomplished through innovative technologies such as augmented reality and machine learning techniques. The functioning of the app is very simple. The points of scientific interest are identified and displayed on a map. By clicking on each of them, it is possible to activate a navigation path. The element to be framed is also shown once the PoI is reached, and this allows the user to access scientific content in an augmented reality format. The access to the content is innovative and is directed by framing a physical object, which may be, for example, an architectural element or a landscape. Within the app the information flow is not unidirectional. If the user notices some elements capturing his/her curiosity, he/she can use the functionality of the Scientific Reporter to give us notice, sending us images, text, and position information. In this way, exchange with the users will be encouraged so that the information can grow and be updated also based on the experiences of the users. HUSH is not limited to urban contexts but can also be used in natural ones too. One of the advantages of this approach is that traditional analog panels and QR codes are avoided. It is well-known that these media deteriorate, can be damaged, and need constant maintenance. Another point in favor of HUSH is that the visitor can be an active player in the process of recognition and in building the contents of the application, not just a simple user. To date, HUSH has already been used in several events involving people of different ages and education levels, with great success. During these testing events HUSH showed only one weakness due to difficulty, reported by a small number of users, in acquiring target images for some PoIs, in particular where well-defined architectonical or artificial elements were missing. In particular this was true close to natural features that changed over time (i.e., trees). This feedback has been taken into account for improving the targets and the database with other images acquired during different time periods. HUSH was used as a tool for urban trekking dedicated to schools of every order and degree, improving the simple oral descriptions. In one of the events involving citizenship, HUSH was used for a treasure hunt where descriptions of PoIs helped in finding the sites needed to achieve the ultimate goal or find a treasure (Figure 9). The event gathered positive acclaim and fostered interaction between visitors and knowledge acquisition.