The Baltic Sea region in the Early Middle Ages formed the zone of contact between the Scandinavian kingdoms, the Frankish Empire, and the Baltic and Slavic tribal areas. In this period a socially, ethnically, religiously and economically heterogeneous area came into being that afforded excellent opportunities for accessing new markets and disseminating innovations. Beginning in the 8th century the Baltic region witnessed a flourishing of long-distance trade and the development and consolidation of a trans-regional transport network. The central element in the organization of the exchange of goods in the Early Middle Ages consisted of coastal settlements that specialized in trans-regional trade and crafts and were established throughout the Baltic region from the 8th century onwards. In the Slav-populated area between the Bay of Lübeck and Gdańsk Bay, nine such sites – Alt-Lübeck, Groß Strömkendorf, Rostock-Dierkow, Ralswiek, Menzlin, Wolin, Szczecin, Bardy/Świelubie, Janów Pomorski – have been archaeologically verified so far. On the basis of historical tradition and archaeological records as well as theoretical considerations, further settlement sites may be supposed in the vicinity of Oldenburger Graben (Starigard/Oldenburg) and Barther Bodden, on the island of Usedom, in the Oder estuary area near Kamień Pomorski and in the Parsęta estuary near Kołobrzeg and in Gdańsk at the mouth of the Vistula.

What we know about the trading posts along the south coast of the Baltic Sea differs very much locally and regionally – which is largely due to excavation on a limited scale and modern-era building. The trading centres began to appear from the early 8th century and some of them grew in importance considerably in the 9th and 10th century. As a result of economic and technological developments as well as changes to the natural environment some of the sites were abandoned or relocated in the course of the 10th century, while others evolved into medieval towns. Comprehensive, primarily interdisciplinary investigations in Groß Strömkendorf, Ralswiek, Menzlin and Janów Pomorski have revealed evidence of an orderly internal structure in the form of villication or the parcelling of land, as is known from other emporia in the North Sea and Baltic Sea region, e.g. Ribe and Kaupang. Data concerning the size of the sites have been acquired in the past decade above all through geophysical surveys.

The maritime trading centres, stations serving long-distance trade throughout the Baltic Sea region and also from the interior, represented important interfaces between land and water, and derived their significance chiefly from the existence of their harbours. The enormous importance of the harbour as an essential economic structure can be clearly recognized from the choice of location for the trading posts, established as they were in sheltered bays and fjords or at riverside sites near the Baltic shore. The topography presented optimal conditions for the siting of harbours and ensured their accessibility for sailing vessels as well as offering protection against storms and raids. The trading centres' survival and development depended therefore on the proper functioning of the harbour. If a harbour became increasingly uneconomical owing to changes in water level or advances in nautical or sailing technology, the harbour or even the entire settlement could be moved to a more favourable locality; in many instances, however, evidence has also been found of large-scale repair and maintenance work as well as enlargements and modifications undertaken in harbour areas.

Archaeological investigations at early medieval ports have been conducted only sporadically between the Bay of Lübeck and Gdańsk Bay. Thus far, archaeologically verified remains of harbour facilities have been found only in Ralswiek on Rügen, Wolin, Szczecin and Gdańsk. In Menzlin, Usedom, Kamień Pomorski, Kołobrzeg and Janów Pomorski, furthermore, infrastructure (streets, bridges), characteristic archaeological find material (boat rivets, wooden dowels, parts of ships) and ship finds indicate the existence of harbour areas, although it is not possible at the present time to make any further statements about their size or construction. In Groß Strömkendorf, analysis of aerial and satellite photos together with geological and geophysical prospecting has yielded proof of a harbour basin. For Rostock-Dierkow, Usedom and Bardy/Świelubie, the evaluation of topographical, geological and pedological charts has brought to light depressions that were presumably highly suitable as places for boats and ships to land during the Early Middle Ages and may therefore have been used as "natural harbours".

As part of the research project Baltic Sea Ports, a systematic and interdisciplinary investigation of the harbour structures of these early medieval emporia between the bays of Wismar and Gdańsk is planned. The first points to be clarified are the extent to which topographical features were decisive for the siting of these settlements' harbours, how the harbours were linked to their respective settlements, what social and economic function the harbours possessed within the settlement structure, and how exactly the loading and unloading of the boats and ships proceeded. Of particular interest is the question of whether riverbank or shoreline reinforcements, moles or wharves were built, and repair, renovation or modification work carried out for this purpose. Against this background, reconstructing the geographical features as well as the environmental processes – such as changes in sea level, the local hydrography, regional/local siltation processes or the shifting of coastlines and relevant waterways as a result of erosion – is of great importance. In the three years for which funding has been obtained (1st project phase, 2012-2015) a comparative evaluation of previously conducted research into early medieval harbours in the area under investigation will first of all be carried out on the basis of the information already existing in the literature, archives and depots. The sites in the area to the west of the river Oder will be in the foreground here. It is hoped that information gaps can be sealed with the aid of geological, geophysical and archaeological survey and analysis methods. Small-scale exploratory excavations will then be conducted to verify the prospection findings and clarify the state of preservation and the dating of any harbour constructions found. Depending on the results, sites located between the Oder and the Vistula will then be investigated more intensively in a second phase of the project (2015-2018). Also, where it is feasible, harbours with well preserved structures will be exposed in representative sections.