Forty-four mayors from some of the most politically and economically powerful cities adopted a common position for the G20 Summit in November in Bali. Gathered under the initiative of the U20 in August in Jakarta, the mayors offered their collaboration and called for action in key areas such as recovery, energy transition, and job market. As governmental actors in an urban world, cities have much to offer and do. Yet they are also embedded in an international system that is defined by nation-states.