The three-year International Summer School on Conservation-Restoration of Wall Paintings - Gradišče Summer School took place over a few weeks in the summer months between 2021 and 2023. The main objective of the project was to plan and carry out conservation-restoration work on the late medieval wall paintings in the Church of St Helena at Gradišče near Divača. Organised by the Slovenian Institute for the Protection of Cultural Heritage, the Swiss University of Applied Sciences and Arts SUPSI, the Academy of Fine Arts and Design in Ljubljana, the Academy of Fine Arts in Zagreb, and under the programmatic guidance of conservator-restorer Albert Felici from the SUPSI University, the Summer School was conceived as an ideal case study on which the most appropriate methodological approach for the conservation and restoration of the valuable paintings was outlined through a close interdisciplinary cooperation. The project was designed for the professional development of conservation-restoration students and professionals working in the field of conservation of decorative architectural surfaces. The activities of each year's programme were outlined in phases and focused on learning about the condition and characteristics of the murals, identifying appropriate conservation and restoration procedures and their implementation. The varied educational programme, carried out by lecturers and experts from the participating institutions, included lectures and presentations of national and international practices, practical fieldwork and professional excursions, which were aimed not only at acquiring new knowledge and skills, but also at getting to know colleagues and exchanging experiences.