The energy services delivered to urban areas in Switzerland make up more than 45% of the national energy consumption. Thus, in the framework of the Tetraener European project, a methodology has been developed to design low temperature thermal networks based on process integration techniques and GIS (geographical information system) database. Water is the renewable energy vector which brings the resource from a lake or river to the end-users. Connecting buildings to the network reduces the external energetic dependency of a given urban area as well as it contributes to reduce the CO2 and other pollutant emissions in a densely populated place. Heat pumps located in the buildings ensure the heat transfer from the district network to the domestic loops. The grid use is versatile since it can either act as a heat source or sink depending on the need (heating/cooling). This work aims for an optimal integration of heating/cooling using pinch analysis for the design and/or retrofit of the network and building temperature control strategy. The combined use of process integration techniques and GIS energy platform is illustrated with the GLN (Geneva Lake Nation) case study. This network located down-town Geneva uses water from the nearby Lake Geneva as an energy source for the surrounding buildings to take advantage of this local resource. Connected buildings to benefit from this sustainable system include those from international organizations. The latter clients have important needs especially in terms of cooling for their large-size conference rooms. The GLN network also acts as a source of non-drinkable water for fountains and irrigation purpose in the surrounding parks.