This book is a compilation of the selected papers from the 2nd International Conference on Building And Simulation (BAS2025). The work focuses on the progress of climate neutral districts and cities, including urban energy systems, sustainable building design, urban climate and smart city simulations and community engagement and replicability of climate-neutral solutions. This book deeply filters available information to map the practical needs for development of climate neutral districts and cities. It provides a guide to our future energy options, outlining the enormous recent changes in the sectors of building, energy and mobility. This book targets a broad readership with interest, experience, and knowledge in energy systems, built environment and urban planning. As such, it will appeal to researchers, graduate students, engineers, consultants, urban scientists, investors, and policymakers, with interests in energy efficiency, energy production, energy flexibility, building/city resilience and climate neutrality.