The Viking Era’s Trelleborg fortresses

by archaeologist and museum director, Ph.D. Lars Christian Nørbach

The Viking Age, and especially the latter part of the eleventh century, appears to be an epoch-making watershed era, characterized by wide-reaching upheavals – not only in what is now Denmark but also throughout the entire Nordic region. The most prominent archaeological testimony from this period is the Viking ring castles that have been found, including Trelleborg (near Slagelse), Nonnebakken (in Odense), Aggersborg (near Løgstør) and Fyrkat (near Hobro). These are the most exceptional layouts dating from the Viking Age in Scandinavia.

The finds are astonishing
The discovery of the Trelleborg layout on Zealand and the subsequent archaeological investigations of the three other fortresses of the same type, which transpired from the mid-1930s and up into the 1960s, constituted nothing less than an outright sensation, which resonated far beyond Denmark’s borders. This was especially because these installations, by virtue of their monumental character and their consistent geometric construction, turned what had been the prevalent understanding of the Viking Age upside down. People had not heretofore been able to imagine such technical and organizational capabilities in early historic times or the existence of such a well-developed political power apparatus as makes itself apparent with these layouts.

Precise circles and right angles
The Trelleborg fortresses are all characterized by a ring rampart with an appurtenant moat and four covering gate openings. The fortresses had a rigorous geometric street system, a division of the internal surface area into four square-shaped blocks. Within each of these square-shaped blocks, there were four longhouses positioned in the form of farmhouses constructed around a quadrangle. All of the four facilities have a uniform and rigorous geometric architecture and a stringent symmetry, which clearly manifests itself in the fortifications’ circular forms and the gate openings’ placement with respect to the four corners of the world.

It has been estimated that the Trelleborg fortresses were built sometime around the year 980 A.D. However, it seems plausible to assume that the fortresses might not have been in existence for very long. And maybe they were operative for only a few years. We are quite sure, for example, that Fyrkat was wiped out after a raging conflagration and that it was not rebuilt.

The same and yet different
Notwithstanding their homogeneity, each one of the fortresses has its own individual constructional features. The diameter of Aggersborg, for example, is 240 meters, which is roughly twice that of the other fortresses.

At Trelleborg, there is a bailey consisting of 15 longhouses and protected by an outer rampart of its own, as well a trench. Cemeteries with remains of the Viking Era have been found at Fyrkat and Trelleborg.

Power’s fortresses
On the basis of their consistent homogeneity and their geometric rigor, it has been assessed that the fortresses once functioned as elements in a larger political power apparatus and military system. We can imagine that the individual houses and yards served to reflect manpower units or ships’ crews and the fortresses’ military function is underscored by the large number of men’s graves and the three mass graves on the burial site at Trelleborg.

Impenetrably thick walls
When one arrived as a visitor to the fortresses, they must have appeared overwhelmingly impressive on account of their earthworks, their thick wooden palisades and their high moats and they probably seemed virtually impossible to conquer.

One moved through the gateway of the fortress and the ring ramparts, from where the guards stood and kept watch on whomever was arriving and suddenly found him/herself standing in the midst of the fortress’s layout, which was teeming with life. Taking the standards of the past into consideration, the houses, measuring more than 7 meters in width and almost 30 meters in length, with their outwardly bulging long walls, must have made their effect on the viewer as large halls of some sort.

When we also take into account that at Trelleborg and Fyrkat, there were four square-shaped blocks arranged around quadrangles while at Aggersborg, there were sixteen such square-shaped blocks with longhouses, it is easy to envision and sense the power that lay behind the construction of these fortresses.

The longhouses themselves were divided into three rooms, of which the middle room measured about 20 meters in length and was, in a number of instances, fitted with a langild (a long Iron Age/Viking fireplace, as opposed to a round or square one). Here the Vikings’ troops were quartered. It was here that they slept, repaired their personal equipment and played games that involved tossing dice.

From several of the halls, shouting, singing and laughter could be heard. But not all the houses were used as residences. From the blacksmith’s workshop, the hammer’s clanking against the anvil mingled with the joyful shouts and inside the storehouse buildings, the arithmetician might have quietly and calmly been busy checking on the army’s supplies – the rations would have to last for the whole winter.

Life inside the castles
The Trelleborg fortresses are not mentioned in any of their own day’s or in any medieval historical sources, which might seem odd when we stop and think about the massive amount of labor that was put into their construction. But when we consider the date that Trelleborg was evidently erected, that is to say, sometime around 980 A.D., it seems likely that King Gorm the Old’s son, King Harald I Bluetooth, would have been involved in the construction of the fortresses here. It is now presumed, accordingly, that the fortresses played a vital role in the amalgamation of the kingdom, a feat to which Bluetooth himself refers on the inscription carved into the large Jelling Runic Stone, which dates from the last half of the tenth century.

The fortresses are situated in such a way that they are well protected from attack by land. But they are also positioned close to the water, near to creeks and fjord inlets, so that ships could be dragged right into the fortress and back into the water again, as need be. Thus the fortresses could be used simultaneously for supervising and controlling trade and as a shelter offering protection from potential enemies. The fortresses could also have fulfilled a function in connection with conflicts outside the boundaries of the kingdom. However, it appears most probable that Trelleborg was a royal power center, which was primarily supposed to secure control over the kingdom’s provinces.

Still a mystery
Despite the fact that 70 years have passed since Trelleborg was discovered, the fortresses and their immediate surroundings still envelop many secrets.

One of the most pressing questions is still the problem of coming up with any proof as to whether or not it was possible to sail up to the fortresses. To this end, the project known as “The King’s Fortress” (website: <kongensborge.dk>) focuses on archaeological studies of wetlands around the fortresses, with an eye to unearthing the possibility of finding traces of shipbuilding and/or the repairing of ships.

Reports of the Nordic countries
Trelleborg, Aggersborg and Fyrkat represent the most prominent archaeological testimony and the most monumental sites dating from the Viking Age on what is the current territory occupied by Denmark. With their grandiose character and their consistently uniform geometric construction, they are truly outstanding and ought rightfully to be considered worthy candidates for inclusion on the World Heritage List.

The fortresses also played a crucial role in connection with gathering the kingdom together, a historical event that the inscription the Jelling Runic Stone describes. Accordingly, they stand as links in the lengthy process that led to the integration of the Nordic countries in the European cultural community and the formation of the Scandinavian nations.

It is now presumed that the fortresses played an important role in the amalgamation of the kingdom, a feat to which Bluetooth himself refers on the Jelling Runic Stone.