The Mapping Sacred Spaces Project addresses the reconstruction of medieval sacred architecture in Southern Italy, with a particular focus on the critical loss of liturgical furnishings and their contextual significance. Through the transformative power of digital humanities, this project embraces interdisciplinary approaches to effectively fill the gaps left by historical damage and the passage of time. Employing advanced digital methodologies, the project meticulously recreates and analyses the interactions between space, objects, and ritual practices, thereby dramatically enhancing our understanding of the region's rich artistic and cultural heritage. Significantly, hermeneutic and heuristic issues arise in creating digital models that aim to fill in gaps. Two case studies pertaining to the Monreale Cathedral and the Abbey Church of Montecassino exhibit both the potential and the limits of digital approaches.