## 1 Introduction
Gamified VR, AR, or MR quests, collecting CH-themed NFTs and DCH souvenirs, foster educational engagement (SDG 4: Quality Education) and drive economic growth (SDG 8: Decent Work and Economic Growth). Online-offline DCH activities can take tourism off the beaten track, and reduce overcrowding while providing digital rewards redeemable on-site for souvenirs, boosting local businesses (SDG 12: Responsible Consumption and Production). AR-guided tours promote cultural understanding (SDG 11: Sustainable Cities and Communities), while post-visits encourage global sharing and partnerships for sustainable development (SDG 17). This holistic approach bridges economy, ecology, education, leisure, technology, culture, and sustainability. XR technologies have shown transformative potential in preserving CH through innovative tools such as digital twins, photogrammetry, and laser scanning. For instance, [PERSON] et al. [12] demonstrated the use of high-resolution 3D modeling to document fragile artifacts and archaeological sites, enabling non-invasive conservation practices. A notable example is the documentation of the Lamalunga Cave and Altamura Man, which utilized digital twins to facilitate remote analysis while avoiding physical damage to the site. Similarly, the PROMETHEUS project [42] highlighted XR-enabled multi-scalar web publishing, allowing for detailed digital preservation and public access to European architectural heritage. Notable examples of how VR is successfully being used to promote and preserve cultural heritage are the British Museum's Bronze Age VR Experience, the Louvre's Mona Lisa VR Experience, the Pompeii VR Experience, Machu Pichu 360\({}^{\circ}\) Virtual Tour, the Acropolis of Athens Virtual Tour, the Nefertari's Tomb VR Experience, the Venice Biennale VR, and the Anne Frank House VR Tour. The British Museum developed a VR experience called \"The Virtual Reality Weekend,\" allowing visitors to explore the Bronze Age in an immersive way, showcasing ancient objects and their historical context. The Louvre introduced a VR tour of [PERSON]'s Mona Lisa, offering visitors an up-close and interactive experience of the iconic painting. VR technology allows users to explore the ancient Roman city of Pompeii as it existed before the eruption of Mount Vesuvius in AD 79. A 360\({}^{\circ}\) VR experience of the UNESCO World Heritage Site Machu Pichu offers users the chance to walk through the ancient Incan citadel remotely. The VR reconstructions of the Acropolis of Athens Virtual Tour allow visitors to experience the Acropolis and its monuments as they appeared in ancient Greece. An immersive VR experience developed by Curiosity Stream lets users explore the stunning tomb of Queen [PERSON]. The Venice Biennale VR art exhibition uses VR to showcase virtual pavilions, art installations, and cultural performances. The Anne Frank House VR Tour provides a virtual tour of the secret annex where [PERSON] and her family hid during World War II. The [PERSON] AR use case illustrates a Web3 physital tourism app that merges cultural heritage (CH) learning, 3D visualizations, and XR for edutainment. Users can earn credits within the app, redeemable for perks at local CH sites, such as museum souvenirs or discounts at nearby restaurants and hotels. This model showcases how CH XR can support hybrid economies through multi-actor collaboration and token-based incentives. Several organizations are actively developing Web3 CH XR applications. CyArk creates 3D models of endangered cultural heritage sites for preservation and education. Google Arts & Culture provides virtual museum and site tours to support global cultural access. The SITE Network promotes immersive XR tourism through a hybrid economy model, aiming to democratize travel and boost local tourism awareness via VR/AR experiences. The core of these experiences sees XR mix with blockchain to create an open interoperable spatial web.