Europe, perhaps more than any other region in the world, is characterised by the presence of border cities and conurbations, urban areas whose morphological and functional continuity can be felt across one or several national borders. In 2010, the ESPON METROBORDER programme thus identified some 40 urban communities within the European Union (EU) and on its borders. However, the dimension of towns and borders has long been neglected, by the states as much as by the European Union. And yet, as part of the regime specific to internal borders, those urban spaces are emblems and vectors of European integration on the local scale. This chapter demonstrates how border cities have been an essential part of the European integration process since its very beginning and how their contribution has been fostered by the EU’s regional policy programmes, especially since the 2000s, helping them to be recognised as specifically dynamic urban border spaces and to use this label in order to develop a multitude of cross-border projects.