International borders are a crucial element in the construction of modern states. The emergence and transformation of border cities is linked with the opening of bridges and other infrastructure of the international circulation system. Thus, these urbanized spaces highlights as required steps for legal and illegal flows of goods and people. There, is given a singular joint between different scales mobilities and a constant contradiction between fluency and firmness, as also between local interests and imaginary, compared to national and continental. We will present a theoretical and methodological discussion aimed to develop some analytical tools to study the joints between international border, mobilities and urban local dynamic. After we will outline a brief descriptive picture of the agglomerations located at the international borders of southern South America, focusing on Argentina, with a view to a future cross-border agglomerations characterization. Finally, we will develop an evaluation of the role of the continental mobility system in the formation of interstate borders and in the emergence and transformation of agglomerations; the current relevancy of the border condition in the urban local configuration and in the current sociocultural complexity; the local hierarchy of the function of node of transport and his scopes in the international transport system.