This thesis investigates how the Greeks used inscriptions in stone to create a sense of community between cities in the third and second centuries BCE, across the borders of kingdoms competing for dominance over the Mediterranean. Interactions between cities were often recorded in long inscribed decrees on standing stone plaques, placed in central urban spaces. The research focuses on three aspects of the role of these inscriptions as media: the words used to describe the relationships between cities; the spaces where they were set up; and public events mentioned in the inscriptions. The inscriptions used language that emphasized belonging and solidarity, even when this did not necessarily reflect reality. They were grouped in specific sanctuaries or other places, to design urban spaces where cosmopolitan connections could be actively experienced. The connections recorded in inscriptions were broadcast at public festivals, assembly meetings, or other events, so that everyone could know what the stones described. Importantly, both inscriptions and events concerning relationships were strategically mirrored: inscriptions often had multiple copies in different cities, and similar versions of public events were often staged in connected cities. This helped to share knowledge among citizen communities, contributing to effective coordination of action over city borders. This strategic use of language, spaces and events in and around inscriptions contributed to creating a universal cosmopolitan experience, helping to maintain a Greek sense of community across royal influence spheres. In the absence of superfast communications technology, inscriptions could serve as media of cosmopolitan connectivity.