This article, as part of the ‘SUMcity’ research program, aims to give a comprehensive account of the regeneration that occurred in Athens by the adaptive reuse of the old FIX Brewery to house the new Hellenic National Museum of Contemporary Art (EMST). Adaptive reuse is an urban sustainability development evolving process, used to manage assets and resources efficiently, resulting in economic development, increased local attraction, and revitalized community engagement. Other than that, modern societies experience the dynamic stream of social media and smart city initiatives, amid a long-discussed and complex cultural heritage preservation backdrop. Notwithstanding the value added to the city, the interaction of sustainable development with adaptive reuse projects, culture, tourism, social media use, and smart city initiatives, along with the impact of this intangible relationship, has yet to be set in a more tangible form. Methodologically, a newly developed conceptual framework is used in order to re-define the (cor)relations among the existent concepts of sustainable development, smart city and cultural heritage. Subsequently, a primary questionnaire-based research is conducted on Instagram users’ geotagging the Hellenic National Museum of Contemporary Art (EMST), analyzing their views in an attempt to demonstrate the arising local potential and sustainability.