ACUUS 2025 Belgrade, the 19^th world conference dedicated to urban underground space, was successfully held in Belgrade and gathered more than 250 participants from 23 countries. The organizing team, composed of the University of Belgrade, the Faculty of Transport and Traffic Engineering, the Urban Planning Institute of Belgrade, and the Institute of Architecture and Urban Planning of Serbia, set high standards and brought the global ACUUS community to Serbia for the first time. This positioned Belgrade as a city ready for an active role in the advancement of underground urbanism and international professional cooperation.

Main aim of the Conference is to engage with all stakeholders in an open and constructive discussion about the further development and improvement of the use of the UUS and its progress towards its recognition and implementation in the current municipal and legislative systems. It is certain that an adequately planned and utilized UUS contributes to the creation of a sustainable, resilient and livable urban environment, which can respond to many challenges a modern city would face including the urban population growth, impacts of climate change, environmental issues, and others. The theme of the Conference was “UNDERGROUND MOBILITY AND ELEVATED THINKING: NEW OPPORTUNITIES AND CHALLENGES IN THE USE OF UNDERGROUND URBAN SPACE” and emphasized on the issues related to swift transportation trough underground infrastructure and in new potential used of underground space, along with its integration to the city functions. The main program covered a wide range of topics, from climate resilience in underground structures and tunneling and construction challenges, to advanced technologies, architectural and urban design solutions, safety and human factors, legal frameworks and property issues, as well as digitalization and artificial intelligence. This diversity enabled interdisciplinary exchange, one of the core values of ACUUS conferences and a key reason why international interest continues to grow. A particularly strong impression was left by the panel session “Integrating Urban Underground Space into Institutional Practice”, held on 5^th November. The panel brought together experts from Japan, Singapore, China, the United Kingdom, and Serbia, opening important discussions on institutional continuity, high-quality 3D databases, regulatory frameworks, and effective coordination among stakeholders. The panel concept was developed by architect Nemanja Sipetic and Prof. Danilo Furundzic, and the conclusions, to be published as a separate document, represent one of the most concrete outputs of the conference. Great interest was also generated by the technical excursion at the Urban Planning Institute of Belgrade (URBEL). URBEL and its collaborators prepared clear and highly professional presentations on the development of the metro system, underground garages, tunnel corridors, and other strategic infrastructure systems. International participants emphasized that the quality of presentations and professionalism of URBEL were fully aligned with the standards of major global events. The main message of ACUUS 2025 Belgrade remains clear. Underground space is no longer a secondary layer of the city but a strategic one, shaping mobility, resilience, energy efficiency, and overall sustainability. The conference showed that Serbia has the expertise, professional capacity, and institutional support to plan underground space responsibly and to actively contribute to shaping international standards in underground urbanism. The entire conference is accredited and the best contributions in form of technical papers will be published in Tunneling and Underground Space Technology (TUST) Journal. For more information and news about the conference you can visit the ACUUS 2025 BELGRADE Conference website