The circular fortress
The Viking fortresses were defensive places where Norse men could prepare their explorations, raids and commercial expeditions and withdraw to afterwards.
Situated near the west coast of the Danish island of Sealand (Sjælland), the Trelleborg fortress is a ring fortress among others in the country. Let us mention, for instance, Aggersborg by the Limfjord in the north of Jutland (Jylland), Fyrkat in Jutland as well and Nonnebakken in Funen (Fyn). All of them are located in river valleys and close to the coast. This proximity is obviously linked to a society focused on shipping.
Architecture of Viking's fortresses
The architecture of all fortresses followed a very similar symmetrical plan. They consisted of a circular rampart which was divided into four quarters by two perpendicular streets crossing at the centre and leading to four gates. In each quarter stood one or several blocks of four houses arranged in a square. Each house could easily accommodate 75 people, that is to say 1200 at least.
The four gates faced the four compass points. As Vikings used to navigate according to the run of the sun or stars, particularly the North Star, it was easy for them to find the geographical compass point directions. They had only to project the direction of either the midday sun or the North Star on the horizon.
The strong similarity between all the fortress plans lets us suspect the existence of common points beyond their defensive purpose alone. That can only be due to the strict layout and orientation of the fortresses.
The construction of Trelleborg dates back to the period 980-1000 of our era. The fortress is situated on a peninsula that juts into a wetland area between two streams. The streams unite into a river which empties into the Great Belt strait (Store Bælt). The fortress was also connected to the Great Belt by a lake that has since disappeared.
Trelleborg is unique with its outer extension which contained fifteen houses protected by another rampart shaped as an arc. They could have housed 1000 people.
As the largest fortress known in Denmark, Trelleborg brings some of the most significant aspects of the Norse tradition together.