The Multimedia Guide mobile Application of the Museum of the Treasure of St. Januarius is a technological tool to present to the museum visitors the stories of devotion to the Patron Saint of the city of Naples through the masterpieces of Neapolitan goldsmith’s art. Devotion, religiosity, spectacularity, this and much more encompasses the Museum's exhibition along a seven-century path that can be admired thanks to the work of custody of the Excellent Deputation of the Royal Chapel of the Treasure. The information content of the mobile Application is conveyed in a dynamic way and the storytelling is guided by the voice, accompanied by an original musical carpet, of an exceptional narrator: Philippe Daverio. In addition to audio tracks and gallery details of the works on display, the mobile Application interfaces with the Beacon (Bluetooth Low Energy) indoor tracking system. This technology creates a direct interaction with the device on which the App is installed, locating the visitor along the visit path and proposing contents dedicated to the different points of interest (POIs) identified on the route, guaranteeing an easy and engaging user experience. In this way users, even if they are not accustomed to the use of technology, can easily access the contents and find their way around the museum. The Multimedia Guide also presents in-depth contents activated in Augmented Reality that integrate information on some POIs in a new and immediate way. By framing some predefined images, or markers, with the camera of the device it is possible to activate contents that reveal details and curiosities about the artwork.