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The Trelleborg fortresses

Date of Submission: 08/01/2010
Criteria: (iv)
Category: Cultural
Submitted by:
Heritage Agency of Denmark
Coordinates: N56 59 43 E9 15 17
Ref.: 5475
Word File

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Property names are listed in the language in which they have been submitted by the State Party



Aggersborg N56 59 43 E9 15 17

Fyrkat N56 37 23 E9 46 13

Trelleborg N55 23 39 E11 15 55


The Trelleborg fortresses include Trelleborg near Slagelse, Fyrkat near Hobro, Aggersborg near Løgstør and Nonnebakken in Odense, of which only the former three have been preserved for posterity. The Trelleborg fortresses are characterised by having a circular rampart with a moat and four roofed gates. The fortresses have a severely geometrical street system, the inner area being divided into squares, each with four longhouses arranged in a quadrangle. The architecture of all four fortresses is uniform and strictly symmetrical, as clearly illustrated by the circular shape of the fortifications and the location of the gates at the four points of the compass - apparently without regard to the terrain.

Dendrochronological tests and C14 tests have shown that the Trelleborg fortresses were built around 980. But the fortresses probably did not last very long, perhaps only 10 to 20 years. For example, Fyrkat was destroyed by fire and was not rebuilt. As the Trelleborg fortresses were all built around 980, they have traditionally been linked to Harald Bluetooth's efforts to unify Denmark and Norway and make the Danes Christian in accordance with his runic stone proclamation. Another interpretation links the fortresses to the conquest of England and therefore to Harald Bluetooth's son, Sweyn Forkbeard. Whatever the case, the fortresses must be viewed as a monumental and military manifestation of the central power of the late Viking era.


Research and dissemination in outline.

Following the recognition in the 1930s of Trelleborg near Slagelse as a fortress complex of the past, an archaeological excavation of this discovery and the three other fortresses was subsequently carried out and completed by the mid-1960s. The archaeological excavations are documented in several monographs and articles of a high professional standard. Apart from minor exploratory digging, no further archaeological investigations of the fortresses themselves have been conducted after the completion of the extensive archaeological excavations. However, since 2007 the Royal Fortresses project has focused on excavations in the wetlands near the fortresses in order to possibly relate the fortresses to the naval power of their time.

The three fortresses are all listed, and they are owned by the National Museum of Denmark (Trelleborg and Fyrkat) and the Danish Forest and Nature Agency (Aggersborg), respectively. Together with the local authorities, these institutions are in charge of the necessary management of the fortresses and adjoining areas.

On completion of the excavations, work was carried out at Trelleborg and Fyrkat to mark the ramparts, moats and holes for posts from the fortress longhouses. At Aggersborg this work was restricted to the ramparts and the moat. In addition, a reconstruction of a longhouse was built outside the Trelleborg fortress complex in the early 1950s and at Fyrkat from 1980. Besides, a museum was built at Trelleborg in 1995, presenting the finds from the fortress and finds from the Viking era in general. A small complex of reconstructed Viking era houses was built next to the museum. About one kilometre from Fyrkat a reconstruction of a Viking era farm from the time of the fortress was built from 1992 to 2002. Information about both the farm and the fortress is presented here. A small museum was erected at Aggersborg to accommodate an exhibition about the fortress and its age, as well as welfare facilities.

The three preserved fortresses all form part of the recreational areas of their respective regions. Signposts have been put up, and other material to guide visitors is available. Good access, parking and welfare facilities are provided at the fortresses, although the quality of the facilities varies from fortress to fortress.

Individual elements of the property and their mutual relationship, including to the landscape.

Today, the visible elements are the fortifications, which include the ring fortress and the related defences and, at Trelleborg, a perimeter fort and moat. The original ramparts consisted of a complex oak-wood structure with an inner skeleton and outer lathing. As any buildings on the parapet and above the gates can only be reconstructed on a hypothetical basis, the fortresses are only visible in the landscape today in the form of reconstructed embankments without woodwork or moats. In addition, reconstructions of the longhouses traceable in the fortresses have been built at Fyrkat and Trelleborg, respectively.

The fortresses are all located in landscapes typical of their respective regions, in river valleys and relatively close to the coast. At both Trelleborg and Fyrkat extensive nature restoration projects have been conducted over the last decade in order to recreate the natural conditions prevailing at the time of the fortresses. The landscapes surrounding the fortresses thus clearly demonstrate the strategic location of the fortresses and the military reasons for building them at what must be described as Viking era junctions.

Justification of Outstanding Universal Value

Justification of the significance (in terms of cultural history) of the property in a North-European or global perspective.

The ring fortresses, Trelleborg, Aggersborg and Fyrkat, represent the most prominent archaeological evidence of the monumental defences of the Viking era in present-day Denmark. No contemporary counterparts exist in either the Nordic countries or Europe. The fortresses should probably be viewed in relation to the unification of Denmark and Norway referred to on the large runic stone in Jelling and therefore as part of the lengthy process that resulted in the integration of the Nordic countries into the European community of culture and the establishment of the Scandinavian states. Furthermore, having been built around 980, the fortresses should be viewed in relation to the contemporary expansion of Dannevirke, which forms part of the transnational application for inscription on the World Heritage List.

Statements of authenticity and/or integrity

Archaeological investigations of large parts of the fortresses have been conducted and presented in several scientific publications of a high standard. The archaeological investigations documented that the fortresses were largely unaffected by later use, apart from cultivation. Following the archaeological investigations, the collapsed ramparts at Trelleborg and Fyrkat were marked in the terrain, and the moats were cleared. At Aggersborg, where the original embankments had to a wide extent been levelled by ploughing, the rampart and the moat were re-established. All these works and the marking of other structures inside or near the fortresses were conducted on the basis of the complete and detailed documentation provided as a result of the excavations.

In connection with the final submission of an application for inscription on the World Heritage List, efforts are being made to provide a general overview of the management and dissemination plans, establishing whether the fortresses are affected by development-related conditions and their status in terms of management.

Comparison with other similar properties

No similar fortresses from the Viking era exist. Therefore, it is hardly possible to tell what inspired the construction of the Trelleborg fortresses.

The Trelleborg fortresses cannot be viewed in isolation; they must be considered in a historical context that includes the Jelling burial mounds and the Kovirke defences at Dannevirke. Jelling should be considered because the construction of the Trelleborg fortresses is traditionally ascribed to Harald Bluetooth, who buried his parents in Jelling and erected a runic stone for them describing his own achievement of consolidating the realm. It is believed that the Trelleborg fortresses were of great significance in this respect.

Based on the straight line of Kovirke and its C14 dating to the time around 980, this defence embankment located a few kilometres south of Dannevirke is considered to have been constructed at the same time and possibly by the same builder as the Trelleborg fortresses.