Harbours serve shipping when it is not on the move. They are structures that, on the one hand − as seen from the water − are the termini of shipping lines operating in regional and supraregional transportation networks. On the other hand − as seen from the land − they are the termini of logistics, by which people, goods and ideas are transported over areas both large and small. Harbours are thus unique interfaces between land and water, between the sea and the mainland. They link two systems that, by their very nature and in the challenges they face, could not be more different.

Ships are the medium in this communication web. They depend on technical facilities and logistical structures that permit the loading and unloading of a wide variety of goods, and that also ensure they are properly maintained and supplied. Whether on oceans, seas or inland waterways, the vessels are efficient and fast links between different areas and even continents. Rivers are major routes connecting the hinterland, where small-scale river traffic can reach even further along minor streams. Indeed, up until the modern era, waterways were the preferred transportation routes: a number of sources provide evidence that they were clearly less expensive than land routes. Harbours can therefore be seen as both logistic and technical phenomena, which, on the one hand, are dependent on the specific geographical constraints of the sea and rivers, but, on the other hand, are the backbone of highly diverse regional and supraregional transportation networks. Although harbours, more than any other element, represent the immediate interface between water and land, their investigation has remained − even today − a research desideratum.

On the one hand, the SPP intends to continue various trends in the chronologically and geographically widely diversified European research on harbours, to place it in an interdisciplinary framework and develop it further methodologically. On the other hand, scientific tools that can survey and confirm the existence of previously unknown harbour features will be further developed and tested. On the whole, the SPP will concentrate on harbours that were primarily used for civilian purposes, but without specifically avoiding or excluding military facilities and any interface between the two uses. Nevertheless, facilities that served only military purposes will not be included.

The study area covers the whole of Europe in its geographical entirety. The extent of the study area is thus bounded in part by the ocean and the seas of Europe (Atlantic, Mediterranean, North Sea, Baltic Sea) with their maritime harbours. Similarly, the navigable rivers of Europe − such as the Rhine, Rhone, Elbe, Oder and Danube − and their tributaries are also of importance because they link the North and Baltic Seas with the Black Sea and Mediterranean, and their inland harbours lie at the heart of regional networks. These riverine areas are in turn gateways to the resources of the hinterland and also permit the wide-spread transfer of goods. Harbour facilities are therefore fundamental parts of the infrastructure.

The time span chosen ranges from the time of the Roman Empire to the 13^th century. Of course, the chronological and geographical limits of the study area thus defined are somewhat blurred and their potential importance in our understanding of the observed phenomena and the generation of comprehensive interpretation models has to be examined on a case by case basis.

So far, when seen as a whole, the development of the individual regions and periods give the impression of being isolated, that they bear no relation to each other. At first glance, the Mediterranean harbours, with their centuries-old tradition, do not seem to be either structurally or functionally comparable with the contemporaneous inland-shipping infrastructure in the Roman provinces; or with the maritime trading centres that developed in northern Europein the early Middle Ages. However, archaeologists specialising in shipping can, in fact, see historical technological connections between the Mediterranean world and the regions to the north of the Alps. The historical and archaeological evidence of long-distance trading also demonstrates the possibility that knowledge of the structure and operation of harbour facilities was transferred.

These distinctly separate regional and chronological approaches were, to our mind, the result of specialisation in the historical and archaeological disciplines: scholars work in their individual fields − prehistory, classical archaeology, archaeology of the Roman provinces, ancient and medieval history, Byzantine studies. The singularity of the SPP is the combination of several different academic cultures and research traditions. The more general formulation of the research topics and the fundamentally uniform methodology mean that the different sources can be correlated to facilitate a search for common interpretations. Tight coordination and the involvement of the relevant natural sciences, including those specialising in maritime matters, will contribute to a successful outcome of the SPP.