In spite of fairly intensive study of the Viking Period, knowledge of Harbours and trading-places from that time, as well as of the level of trade and its organization, is very limited. The best examples of early trading Centres of this kind are Birka, Hedeby, Grobin, Wolin, Paviken and others. A main source of error in the discussion of Baltic trade in the Viking period is obviously that the majority of investigations of Harbours are of such places as are known from written sources. The "normal" idea is that trade in the Baltic area was mainly between these well-documented places.
For instance, a map of the Swedish coast showing trade routes and trading places we know of from written documents or which have been discovered by pure chance, gives a much too simple picture of reality. We should instead calculate with a vast number of Harbours and trading places all around the coast. For instance there is, remarkably, no well known Harbours and trading-places as Birka or Paviken along the coasts of Östergötland and Småland, despite that the central part of Östergötland is one of the largest, oldest and most important cultivated areas in Sweden outside Skåne. It is not reasonable to believe that the farmers on the Östergöta-plateau went to Birka to buy goods from the south when the merchants passed the coast of Östergötland on their way to Birka.
In other words, there ought to have been many more Harbours and trading places along the Baltic coast; from small fishing camps to large and important trading places, more or less permanently occupied, where manufacture of jewelery, trade and building/repairing ships were carried out.
On the island of Gotland the excavation at Paviken in the parish of Västergarn, together with place-names such as "Snäck-" (Olsson 1979, 1994) and the distribution of the so-called "kastaler", defensive towers, suggest that these sites in the Viking Period formed part of an organized society. The idea is that there were central harbours/trading ports in the Viking Period, situated one in each "sätting", and consequently six harbours on the island (Lundström 1981).
Medieval society was obviously fairly regulated and there is much in favour of the idea of a system of centralized harbours and trading places in the 11th and 12th centuries. Taking into consideration the way changes in society normally come about, one can put forward the hypothesis that the medieval situation is the result of a long process of development, going right back to prehistoric times.
Some researchers consider that long-distance trade, and thereby the activities along the coast, began in the 7th or 8th century and that it accelerated throughout the Viking Age. At the end of the Viking Period or at the beginning of the Middle Ages, trade was concentrated at a smaller number of trading ports, whose importance increased at the expense of other sites, at the same time as the extent of the activity was enlarged. In course of time, the "administrative" picture also changed, so that the expansion of trading ports, similar to other changes in the society, was a result of private enterprise, and in the Early Middle Age arranged according to a spatial and administrative system.
The idea that the expansion of trading ports was a result of private enterprise leads to the hypothesis that there were a large number of Harbours of different size in the late Merovingian - Early Viking Period.
Bearing the constancy in the cultural landscape in mind, where the districts of the 17th century to a great extent consist of former Iron Age districts (Carlsson 1979, Östergren 1989), one can put forward the hypothesis that on Gotland there was at least one trading port in every parish along the coast in the late Iron Age. That means, if the hypothesis is correct, that we can expect remains from a considerable number of Harbours along the coast of Gotland, as well as the whole of the Baltic coast.
The project "Harbours and trading places on Gotland AD 600-1000"
The project "Harbours and trading places on Gotland AD 600-1000" was carried through during the period 1987-1995. The aim of the project was to analyze and describe the number of Harbours and trading places, their structure, development, spatial organization and development during the period appx. AD 600-1000. Responsible for the project was associate professor Dan Carlsson.
The starting point for the project was the study of archives and old maps of the coastal region. Three criteria have been decisive for localising possible Harbours:
1. Prehistoric graves or gravefields close to the coast,
2. A shore protected from strong winds and
3. A situation in the cultural landscape as seen in the cadastral maps from the 18th and 19th centuries, which diverges from the normal. That could for instance mean roads meeting at a certain point on the coast or that there is agricultural land (cultivated fields and meadows) near the coast but no farm within reasonable distance.
The second and third step in the project involved phosphate mapping of suspected locations, and larger or minor excavations were carried out at about 10 places along the Gotlandic coast where one could suspect remains of activity from Late Iron Age until Early Middle Age with the main point to the Viking Age.
The result was that about 50 places along the Gotlandic coast showed indications of activities during the Viking Age. All of them are just "possible" Harbours and trading places. It is not sure that all of them have the same character, being small fishing camp as well as large trading place, and even some of them might have nothing to do with Viking Age maritime constructions at all.
60 possible Harbours or trading places from the Viking Age along the Gotlandic coast.
On the other hand, it is possible that some Harbours have not yet been discovered depending on the choice of method. For instance, there are surprisingly few Harbours on the East coast, which probably depend on the difficulties to identify Harbours at these places. The East coast is more shelving than on the west side of the island, and that make it more difficult to find the precise place for any harbour.
Perspicuous evaluate of the projects result give us a number of places that can be seen as larger Harbours, divergent from the others because of a rich and varied number of artifacts. To this category belongs Boge, Bandlunde, Fröjel, Paviken-Västergarn and Visby.
On Gotland it is very unusual for a church to be placed very far away from the settlement and normally this only occurs at places where there was much trading activity, as for instance at Boge, Fröjel, Paviken-Västergarn and Visby. The location of the church in these parishes, is in direct contact with the sea and far from the centre of the agricultural settlement to which it belongs. This can be seen as an indication of some important activity going on along the coast