After more than a century since the first appearance of city diplomacy, cities’ capacity to act internationally is no more in doubt. Around the world, the debate shifted from whether cities can act internationally to the limits of their influence. The high rate of urbanization worldwide and the concentration of the world’s economy in a number of global cities are not enough to explain such a trend. Alongside these elements, a major political turn has risen in city halls since the end of the Second World War. Reconciliation, solidarity, regionalism, sustainable development, resilience, and now post-pandemic economic recovery: cities international action has been continuously evolving, guided by their commitment to link local to global. The chapter will illustrate this progressive widening of city diplomacy’s scope and impact, including insight into interaction with other international actors, shifting legal boundaries, and mutating geographies.