This chapter looks beyond the locative AR audio trails of Hidden Cities to consider how the new affordances of mobile devices are enabling more complex and immersive locative experiences of the historic built environment. It outlines the research workflow and underpinning research that led to the creation of Hidden Florence 3D, a 1:1 scale reconstruction of the lost church of San Pier Maggiore (Florence). San Pier Maggiore was one of the most important churches in Florence, attached to a prestigious convent of Benedictine nuns. The church was demolished in the eighteenth century to make way for a covered market and all that remains today is a street of the same name. Its artworks are now dispersed in collections around the world, including Jacopo di Cione’s altarpiece painted for the church’s high altar in 1371, now in the National Gallery, London. The Hidden Florence 3D app enables the user to experience the fourteenth-century church of San Pier Maggiore in Florence, or while viewing its original altarpiece, now housed in the National Gallery. The chapter will also discuss aspects of how the app was used to engage the local community of residents and shopkeepers in Florence, revealing to them the lost church at the heart of their neighbourhood, and so presenting cutting-edge digital humanities research.