HEPHAESTUS develops digital Information Models (IM) and reliable 3D Databases for Cultural Heritage Routes (CHRs) across European border territories, defining collaborative inter-sectoral protocols to enhance the architectural cultural heritage and improve sustainable planning and management processes. It bears on the physical materiality and critical role of fortifications and military architecture – as building complexes that usually embody the emblem of historical geopolitical and societal limits – to turn them into digital systems that unify administrative models across European borders. Military architecture’s paradigms transcend regional characterisations and are based on models that coexist in different countries, lending themselves to generating management systems that overcome borders. HEPHAESTUS brings together historians, architects, 3D modelling experts, software developers, and urban planners in a partnership of universities, research centres, small and medium-sized enterprises, and cultural institutes from Italy, Germany, Poland, and Croatia. The specific and complementary expertise of partners enables the structuring of a multiphase methodology that includes: Digital data acquisition, 3D semantic modelling, models and databases’ association, Digital Twins’ development, open data platforms’ development, and definition of standardised multiscale databases. This project structures a novel way to investigate fortification CHRs according to a scientific model, promoting the digital transition and, on a European level, the development of a programmatic “Charta” of Documentation-for-Intervention, which can be applied on a broader scale. Through Digital Twins based on informative systems, HEPHAESTUS codifies a novel and cutting-edge representative language for the widespread heritage of CHRs. Moreover, it creates potential market opportunities for non-academic participants, thus bringing significant benefits also for European societies/cultures. GdanskTech offers visualisation and digitisation laboratories for the development of experimental digital IM and 3D databases and the integration of digital solutions, which, working in collaboration with twin partner laboratories, create an integrated, transnational network and actively involve the academic community. This in turn will facilitate knowledge transfer, testing and validation of research and real-world work which will significantly contribute to the preservation of CHR.