## 2 Ten Case Studies in Extended Realities for Cultural Heritage Preservation
Additionally, it is a great example of using an A/B test--in this case, comparing an AR version with a VR version in terms of learning retention, with a between-subjects design. A between-subjects design is relevant to cultural heritage CH XR research because it allows researchers to test different versions of an XR experience across distinct groups of users, making it especially useful when the experience itself is likely to have lasting effects or when exposure to multiple conditions could bias participants. In CH XR, where the emotional impact, narrative immersion, or educational outcomes are central, experiencing one version might influence how a user perceives another, making within-subject comparisons less reliable. A between-subjects design avoids this carryover effect and enables cleaner comparisons between different design choices--such as interaction styles, storytelling approaches, or levels of historical accuracy--by ensuring that each participant only engages with one version. This design is particularly important when assessing first-time user impressions, which are often critical in cultural engagement contexts. The Life of a House AR App--This is an on-site AR experience in Tallinn, Estonia, reconstructing the demolished Weigh House digitally with historical context and interactive storytelling. It is a great example of field-based research used to guarantee the ecological validity of the evaluation, and using qualitative data collection from in-depth interviews, with open-ended questions for evaluation with end-users during multiple phases of the development of the app, based on theme-based content analysis. * 7. Fountain of the Lions--This is a museum-based interactive 3D experience at the Alhambra, Spain, letting users explore and manipulate a digital twin of the iconic fountain and its inscriptions. It is a great example of adapting the CW method to 3D, with the 3D CW example. It also uses 3D HE, and is already published in a conference paper. * 8. CHISel Platform--This is a multi-user 3D annotation tool for experts to document, analyze, and collaborate on the restoration and study of digital heritage artifacts. It is a great example of a complex application still under development, and the use of the CW method, which was specifically developed for early stage evaluations on applications that may not be fully functional and not yet ready for testing with end-users. * 9. PLUGGY Platform--This is a cultural heritage social curation platform, potentially Web3-enabled, for users and institutions to co-create and share cultural heritage stories through virtual exhibitions and immersive media. It is a great example of using a carefully created design and evaluation framework that consists of a triangulation of qualitative and quantitative data, i.e., a specially tailored questionnaire which may include the SUS questionnaire, the Net Promoter Score (NPS) questionnaire, and formative and summative evaluations, with multiple end-user types, for the collection of diverse end-user needs. * 10. Picasso AR--This is a VR/AR interactive experience in Malaga, Spain, allowing users to engage in virtual dialogue with [PERSON] and learn about his life in immersive settings. It is a great example of the lean development philosophy and the Design Thinking/Design Doing methodology in action; using the lean MVP pitch deck and lean prototype, the prototype was validated with end-users, competitor analysis, and market research. It clearly demonstrates how a generic method--in this case, the structure and purpose of a pitch deck--must be tailored to fit a specific context or application. While the fundamental elements of a pitch deck remain the same (e.g., a problem statement, solution, market, value proposition, and call to action), the content and style need to be carefully adapted to the particular product or service being pitched. The ten use case studies are organized into four application scenarios, each defined by its specific user context and technological setting.