The book is devoted to borders, cross-border collaboration and cross-border integration, analyzing European border twin towns and continental integration processes as a context for the investigation. Those pairings - towns located on the border and directly neighboring each other - serve as an interesting microcosm where, on a reduced scale, continent-wide phenomena can be observed and tested. Constituting on the one hand exceptions in the territorial-political development of European states, on the other phenomena typically embodying Europe's historic territorial complexity, they are often termed 'laboratories of European integration'. This means they are forerunners of continent-wide processes, where the 'European' idea is tested in micro-scale. At the same time they challenge state boundaries, still one of the most crucial elements of sovereignty, defining the shape of the nation state. The aim of the book is to draw a picture of European integration in a down-scaled perspective by testing the cross border collaboration and integration of border twin towns. The main question raised here is how the European project is implemented on borders at the local level. It is operationalized by the secondary questions: How has the European integration process reorganized the spatial-political order, based on Westphalian principles? How do border twin towns structure their mutual relations? What is the role of the historic legacies in current collaboration and integration? Why and how do the towns integrate? And last but not least, how should the newly emerged structures crossing state boundaries be governed? The author answers these questions by testing 24 border twin towns pairs in various parts of the continent.