Mixed Reality for Intangible Cultural Heritage: Virtual Portals and Hybrid Guided Visits in a Prison Museum

Immersive technologies hold significant potential for enhancing the transmission of intangible cultural heritage, particularly testimony-centered narratives in resonant historical sites. Yet, their effective integration with traditional museum practices remains underexplored. This study presents the design, development, and evaluation of a bespoke mixed-reality (MR) \emph{virtual portal} application at Le Nuove Museum, a former Turin prison museum preserving Italian Resistance memories from World War II. The MR experience employs a modular portal system that anchors witness testimonies within authentic carceral architecture, prioritizing narrative resonance over technical complexity through minimal contemplative interaction. Deployed in a real museum setting, the application mediates hybrid visitor journeys combining immersive mediation with human-guided tours. By employing validated socio-technical scales, intrinsic motivation inventories and engagement measures, this work examines how MR design choices shape visitor engagement, emotional impact, and interpretive synergy with guided interpretation. Findings inform a practical framework for responsible MR deployment in sensitive heritage contexts, emphasizing emotionally grounded, curatorial-aligned design.