In destinations where tourism represents a significant economic and cultural development source, it is crucial to address and mitigate the associated threats and challenges. In this regard, the present study aims to analyze the concept of sustainable tourism. This concept promotes tourism development while protecting environmental resources and preserving local cultural identities. The tool employed for this analysis is the Tourism Carrying Capacity (TCC), a methodology that was initially developed to define the maximum number of visitors a destination can handle without compromising its sustainability. The paper explores the evolution of this concept from both a theoretical and practical point of view, applying the most recent approach. The integrated methodology employed in this study aims to evaluate this concept to propose management guidelines for the management of cultural heritage sites. This paper will apply the methodology to the real-case study of the Sacra di San Michele. This abbey is a site of significant cultural, historical and spiritual value to the region of Piedmont and is currently listed as a tentative World Heritage Site. The results highlight the need to redesign the direct access to Sacra, with a better management of public transport and interchanges between public and private transport. In addition to setting the basis for a balanced management of the site while preserving the environmental and cultural values, this paper aims to demonstrate the importance of adopting integrated methodologies for decision support in complex contexts such as the cultural heritage sites.