Climate urgency calls on all political levels to act more stringent and faster. This proposal is the first to unite cities across Europe to work out actionable, spatially differentiated transition roadmaps to decarbonise heating and cooling for buildings in 2050, taking up the challenge to phase out natural gas in heating. Transitioning the sector to energy-efficient, renewable and zero-carbon solutions is key to meet the EU climate and energy targets. Given the long life-cycles of the grid infrastructures involved, there is an urgency to start the planning of this transition today. But how? What first? Which systems? How to govern this process? Increasing complexity of the energy system together with technological uncertainties require a high level of knowledge and skills to act wisely. Cities are ill-equipped for this. They lack capacity and skills as well as legal empowerment to act. Decarb City Pipes 2050 showcases how local authorities can succeed in this challenge. Bilbao, Bratislava, Dublin, Munich, Rotterdam, Vienna and Winterthur, seven cities from frontrunners to beginners join forces to learn from each other and elaborate innovative responses together. They explore pathways suitable for their local challenges and build up skills in the use of data, planning tools and instruments, techno-economic as well as process and transition management knowhow. In a participatory process with stakeholders, they develop tangible transition roadmaps, building up trust and commitment for its implementation along the way. In deep peer-to-peer exchanges, cities and utilities share knowledge to benefit from other perspectives, stages of advancement and planning traditions. Together, they will advocate for the needed changes to framework conditions. Enriched by a distinguished advisory board, the project aims to empower >220 public officers and improve >50 policies. Ultimately, it strives to motivate and support >80 more cities to start the same roadmap process.