Cities can act as climate solvers if they manage to tackle the huge city challenge of managing optimal usage of their finite and costly space and room for resources. The density of people in the cities are both an opportunity and a huge challenge.   The opportunity lies within the possibility for the many to share climate-effective services – maybe one of the best and most effective climate strategies. The challenge for the city to unlock this potential is the complexity – so many services and features for the many in the same finite space.  We would like to inspire for an open discussion in connection to city management in areas such as energy, city logistics and waste management by sharing some insights and examples on how to move forward with the help of digital twins, IoT and related technologies.