The Trelleborg Viking Fortress covers a total area of 6 ha, which corresponds to 12 football pitches. The structure consists of an inner fortress and an outer ward. The fortress is located close to the confluence of two rivers, the River Tude and the River Vårby, which provided natural protection in three directions. The outer ward is encircled by a rampart, which stretches between the two rivers and thus delimits the whole area between the two rivers. It is thought that for the construction of Trelleborg, around half of all the oak woods on Zealand at the time were felled.
The inner fortress
The inner fortress consists of a perfectly circular rampart, which is c. 136 m in diameter. Four gates provide access to the inner fortress and the gates are connected to one another by two wood-surfaced streets that cross in the middle, together with a narrow, wood-surfaced track along the inside of the rampart. The inner rampart is around 17 m wide and 5 m high. It contains c. 25,000 m3 of earth, stone and timber.
The oak-covered circular rampart was originally almost vertical on the outer side. On top of the rampart there was originally a palisade and it also featured an external archers’ walkway all the way round. Both the inner rampart and outer rampart feature an outer moat. The moat of the inner rampart is c. 17 m wide and 4 m deep. It was not filled with water, but traces of a number of posts have been found at the bottom of the moat, which may have been pointed or else are just evidence of simple planking.
A timber bridge
In the south-east of the area was a timber bridge, which was placed midway between the two main gates to the inner fortress. This meant that attackers had to go the longest possible distance in order to reach the gates and thus were vulnerable to attack. The gates would have been covered, and the solid stone foundations around the gate openings suggest that there were originally timber towers or gatehouses above the gates.
The inner fortress
The inner fortress contains traces of 16 long houses, which are arranged in blocks of 4 houses positioned around a shared yard. In two of these yards, in the north-east and south-west, small, rectangular buildings were located. Near the north and west gates there were also two small, square houses. Traces of a number of other buildings have also been found in the area, but it is unclear whether any of these relate to the fortress and they may not be contemporary. There is also evidence of numerous wells and waste pits.
The outer ward
In the outer ward or bailey are a total of 15 long houses, placed side by side and radiating out to the outer rampart. Two of these houses are isolated: they are located at a distance of c. 30 m from the other houses. There are also traces of other, smaller house types. The outer rampart terminates to the north in a square area, which contained the burial place of the fortress, where 135 graves containing at least 157 people have been found. Most of these were single graves, but some burials contained the remains of several individuals. The grave goods that were recovered were very limited.
The manning of the fortress
It is not known with certainty how many people were stationed at the fortress, but a number of between 500 and 800 is not unrealistic. However, it is also a possible that the fortress was not fully manned in peacetime, but instead contained a smaller garrison, which could be supplemented during times of crisis.
Whereas the houses of the inner fortress were primarily for habitation, the finds from the houses of the outer ward suggest that many of these were stables and workshops. Only the two southernmost long houses of the outer ward contained evidence of fireplaces. The rampart and moat of the outer ward were significantly smaller than those of the inner fortress, and no traces of associated palisades or other fortifications have been found. The outer rampart was perhaps never finally completed. The outer rampart’s moat is narrower and shallower than the inner moat, and no traces of wooden stakes have been identified. Access to the outer ward was available via an opening at the western end of the rampart towards the River Vårby, using a small bridge over the moat.
The long houses
The characteristic long houses are more or less uniform, measuring c. 29.42 m long and 7.90 m wide. The houses have curving walls, and all the long houses of the inner fortress and 9 of those in the outer ward feature a large, 18-metres-long middle room and two small gable rooms. The long houses were constructed entirely of timbers and were supported on the outside by a row of slanting posts. The roof-supporting timbers may have gone down below the ground surface to support the structure of the house.