Fyrkat

Fyrkat is a former Viking ring castle in Denmark, dating from c. 980 AD. It is located near the town of Hobro, some distance from the present end of the Mariager Fjord in Northern Jutland. The fortress is built on a narrow piece of land, with a stream on one side and swampy area on the other sides. It would have enabled control of the traffic on the main land route between Aalborg and Aarhus.

Like the other ring castles (or forts) at Aggersborg or Trelleborg near Slagelse it is designed as exact circle with four gates opposite to each other and connected by two wooden roads that cross in a right angle in the exact middle of the fort. A circle road gave access to the wall. In each of the four quarters stood four Longhouses of the same design arranged in a square with a smaller house in the middle.

The inner diameter of the ramparts was 120 meters and the width at the base 12–13 meters. They were constructed of three rows of vertical wooden poles. Each pole connected to the next ring by beams. The innermost row was the lowest and the gaps filled horizontal with planks forming a wall to the inside of the fort. The middle row was as high as the earthwork and carried the inner side of the walkway. The earth fill sloped to the inside so the ramparts could be easily accessed from every point of the circle road. The outer row of poles was strengthened on the inside and outside with slanted beams at the base. They probably were higher than the middle row and supported a parapet. The gaps between the posts were again filled horizontally with planks but on the outside there was also a wall of vertical trunks slightly leaning to the wall. The space in between the post rows was stacked with some 10000 cubic meters of turf. On the wall there was a walkway made of planks. The outer wall is presumed to have stood some four meters high. The northeast quarter was protected by a ditch with pointed bottom about 7 to 8 meters wide and under 2 meters deep. The ditch on the west and southwest side was never finished. The other sides were protected by a river and rather swampy area. A structure in front of the west gate my have been a gatehouse of some sort.

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