Where does sustainability stand in underground tourism? A literature review

Underground sites have become an attractive tourist destination for an increasing number of visitors. This flow of visitors has made sustainability a major issue, that is, the way in which tourism development ensures economic benefits for host communities and respects local identity without compromising the environmental resources. Many studies have explored sustainable tourism in the Underground Built Heritage (UBH), but privilege the analysis of a single perspective, that is, economic sustainability, e.g., potentialities of cultural routes, or environmental sustainability, such as the impact of visitors on the cave climate. However, some attention has been paid to the social implications of tourism in the UBH, that is, the impacts of tourism development on improving the quality of life of the local community and the enhancement of their sense of community while respecting cultural authenticity. Our aim is to reconcile these perspectives and obtain, through a semi-systematic review, a clear picture of the sustainability of tourism in UBH sites. The aggregation of existing knowledge around the three pillars of sustainability has highlighted the importance of community involvement and collaboration among UBH stakeholders to ensure a balance between the protection and valorisation of UBH, which can also be achieved through networking strategies.