Underground4value (COST Action CA18110) is a four years’ project (2019-2023) establishing an expert network from twenty-nine countries, with the objective of promoting balanced and sustainable approaches for the conservation and promotion of underground built heritage (UBH). Every year, four underground sites and their local communities become places for experimenting studies, new policies, and participatory approaches. During the first year (April 2019 - March 2020), the sites of Naples (Italy), La Union (Murcia, Spain), Postojna (Slovenia) and Göreme (Cappadocia, Turkey) have been selected. The originality of the approach is that it is geared towards assisting local communities’ decision-making with cultural, scientific and technical knowledge of the underground built heritage, from many different perspectives: archaeology, geo-technics, history, urban planning, cultural anthropology, economics, architecture, cultural tourism, ecology.The Living Lab approach is used to organise fieldwork, spending time on each site with a mix of participants (international scientists and local practitioners). The idea is to identify and explore social innovations models for empowering local communities and making them part of the UBH promotion process. Collected information is then the basis for developing new research and training, which remain open and accessible. Knowledge transfer is secured by several dedicated tasks, including a Training School, held in last February in Naples, where the trainees have morning learning sessions and afternoon research activities on specific topics occurred in the living labs’ activities.