This book is a theoretical and ethnographic study of the shifting border between the Republic of North Macedonia and Greece. The central argument is that political borders between states not only restrict or regulate the movement of people and things but are also always porous and permeable, exceeding state governmentality. To support this argument the book draws on scholarship from geology that describes and classifies different kinds of rock porosity. Just as seemingly solid rock is often laden with pores that allow the passage of liquids and gases, so too are ostensibly impenetrable borders laden with forms and infrastructures of passage. This metaphor is theoretically powerful, as it facilitates the idea of border porosities through a varied set of case studies centered on the Greek–Macedonian border. The case studies include: the history of railways in the region, border-town beauty tourism, child refugees during the Greek Civil War, transnational mining corporations and environmental activism, and, finally, a massive, highly politicized urban renewal project. Using interdisciplinary frameworks combining anthropology, history, philosophy, and geology, the book analyzes permeations triggered by the border and its porous nature that underline the empirical, political, and philosophical processes with all their emancipatory or restrictive effects.