Far below the Brenner Pass, the longest underground railway connection in the world is being built. The Brenner Base Tunnel (BBT) system includes about 230 km of tunnels. 157 km have already been excavated. In the context of this project, GEOEG performed a concept study for a cooling system serving the Brenner Base Tunnel. The system consists of exploiting mountain water that further serves with thermal energy for use in buildings in the city of Innsbruck. This intervention derives from the need to have a cooling system for the facility rooms of the BBT to maintain in such environments an appropriate temperature for indoor installations. Such a system can take advantage of the presence of a source of cold water on site. This cold water source, once heated through the absorption of heat from the facility rooms, could then be used as a heat source. The system can be seen as an alternative or a complement to a purely electrical system.