Salt mines, a significant category of local, regional, national, and/or European underground heritage, are becoming attractive tourism destinations. This paper examines three cases of salt mining in different European countries, namely Wieliczka in Poland, Campina de Cima in Portugal, and Turda in Romania. They are analyzed in the context of history, typical attributes of their attractiveness, and new uses after the salt extraction was or is going to be stopped, in order to detect their unique values as important assets for both Underground Built Heritage (UBH) and Salt Heritage Tourism (SHT). The results of their comparison show that despite a positive impact related to their protection as cultural and industrial heritage, there are also some negative aspects related to increasing costs of their maintenance and adaptation of salt mines to new functions and to meet the tourism needs. By putting in place measures to enhance the awareness of their values and for activating the local community, the three mines are showcases for the economic outputs for their sites and regions, as well as for increasing knowledge regarding UBH.

The scarce knowledge and documentation of Underground Built Heritage (UBH) assets frequently limit their full exploitation and valorization. The aim of this work is to reflect on the techniques, functions, and technical features of a specific case study in a very broad context that can, however, be a building block for the understanding, preservation, and reuse of architectural and engineering values that represent a fundamental trace of the history of a society. Therefore, to fill these knowledge gaps, it was constructed a 3D GIS model, multi-scale, and interoperable database, capable of management, promotion, and valorization of UBH. The case study focuses on the old water supply system of the city of Lisbon, as UBH site, with galleries and cisterns that are points of connection with the urban environment above. For the creation of 3D models of the structure under investigation, it was decided to carry out a survey with Mobile Mapping System as a first step, which allowed the construction of a dense point cloud useful to build 3D models of individual objects. Finally, the 3D models were imported into the 3D GIS environment and multi-information could be linked for each previously identified element for greater knowledge sharing. This research has demonstrated how geomatic techniques can be effectively used in conjunction with the information management systems of GIS to explore this “hidden” heritage and has highlighted the limitations and problems of 3D digitization of the UBH. The results obtained offer the possibility of extending and adapting the methodology to different application contexts and the possibility of customizing the data representation.

Participatory budgeting has arisen as an interesting form of citizen participation in urban development and, thus, as a new way of exercising placemaking and grassroots democracy. In this article, we provide an analysis of projects in Lisbon (Portugal), Valencia (Spain), and Warsaw (Poland) with a focus on three key projects concerned with improving the public realm and their contribution to enhancing the network of public open spaces. Our guiding question is: What are the potential benefits of participatory budgeting to increase green spaces and urban governance? A comparison of the three cities’ participatory budgeting programmes provides an overview of their social and political goals and the contents that provide opportunities for citizens’ participation in decision-making. The cases of Jardim do Caracol da Penha (Lisbon), the Green Street Świętokrzyska (Warsaw), and the Green Plan for the Poblats Marítims District (Valencia) pave the way for a discussion on engagement, empowerment, and connectivity with the local communities through public spaces. Using participatory budgeting as a planning and political instrument at the municipal level, as the three cases show, can be a useful way to enhance and enrich the communities’ engagement with their environments. One aspect that emerged is the communication strategies implemented in the three cases. The analysis shows that the use of media and social networks to disseminate information and gather supporters for their ideas and this growth in political influence seems to be essential for participatory budgeting. The study is backed by desk work (comprehensive understanding of the local programmes) and field work to better identify the changes in loco.

This paper delivers actionable recommendations towards building a rationale for activating and promoting Underground Built Heritage (UBH) based on the nexus heritage, territory and society, and making use of existing literature and findings from five international cases. The research was conducted in the framework of the working group on Planning Approaches of the COST Action Underground4value. The analysis of the cases aims to provide guidelines for this working group and to benchmark good practices in activating UBH. It highlights the importance of community-led initiatives, leadership and dialogue and power sharing between the local/regional authorities and communities aiming for better understanding of the potential of UBH. The successes and/or failures of the five cases emphasise the importance of knowledge and experience in participatory approaches. Success was verified, when effectiveness and democratic principles were combined in the planning process, and local history is integrated with citizen science, co-creation and placemaking. The analysed approaches stimulate a new hybrid layer for activating UBH, provide mechanisms of mediation between people and heritage, and contribute to cultural and social dimensions of sustainability. This is a highly challenging endeavour, as it seeks to support and advance a sound understanding of UBH as a sustainable resource, backed by strategic stakeholder dialogue and contextual knowledge. Such effort requires a dynamic understanding of UBH values, knowledge, abilities and skills, towards creating more effective coalitions of “actors” within localities, by developing structures, which encourage long term collaborative relationships.