ABSTRACT
Among the host of internal borders within Spain (i.e. non-state borders), the boundary between the autonomous communities of Catalonia and Aragón is unique. It is one of the oldest (reputedly established in 1305, although its origins may well predate this by a number of centuries) and most firmly entrenched of all boundaries, given that it has not undergone any changes in the intervening centuries. Since first being drawn, the border has witnessed many significant events including the creation of the kingdom of Spain (1479), the administrative organisation of the state into provinces (1833) and subsequently into autonomous communities (1978). Yet, through all these upheavals the border has remained intact. Its uniqueness from a territorial perspective stems from the fact that its northern half (approximately 140 km) coincides with the course of one of the main rivers of the Spanish slopes of the Pyrenees: the river Noguera Ribagorzana (which flows into the river Segre and ultimately into the river Ebre). This would be of little significance if it were not for the fact that in most of the valleys of the southern slopes of the Pyrenees, it is the rivers that constitute the primary communication channels: the link between those living on either bank. The peoples of the valley form one community with strong, deeply rooted functional and social ties.
