During the year of 980 there was the biggest construction effort in Denmark up until this time. It was a time of turmoil with a strong German Roman emperor ruling just south of the boarder. This might have been the reason the Danish king Harald Blåtand (Bluetooth) started these buildings. He was the first strong king ruling all of Denmark and able to such a construction effort across the Danish territory. Previously the kings had primarily been local kings who only ruled part of what Harald took over.
The fortress was built very quickly within a year or two and disappeared almost as quickly. they only lasted for 5-20 years before they were abandoned – possibly because the German emperor die and were succeed by a young child who were no threat against Denmark.
The construction of his fortress was a massive effort. The smallest had a diameter of 120 meters and a dirt wall protecting the fortress. Within the smaller fortresses there were 16 big wooden houses that could accommodate hundreds of people in total possible upward of a thousand men. This would be a formidable army during this period of time.
The Viking ring fortress was constructed at strategic important locations around Denmark. The biggest of them were Aggersborg and it was located at a narrow passage of Limfjorden. From this location it would be possible to control the travel along the fjord which connects two important bodies of Danish waters namely the North Sea and Kattegat. Aggersborg is also close to the import ancient road called Hærvejen or Army road which were one of the few main roads in Denmark at this time and were used to transport armies over land instead of by ship.
Aggersborg was bigger than the other ring fortress – actually it was four time the size of the normal fortress with a diameter of 240 meters instead of only 120 meters. Inside the ring of the fortress there was not the normal 16 long houses but 48 houses – hence this fortress could house a formidable army if all the houses were full.
Unfortunately there isn’t a lot to see when you visit the present day Aggersborg. The heyday of the area is long pass and now there is only a small village nearby – I guess this is part of the reason the area has been preserved there has been no need for later development on the ground.
We drive up to the parking lot next to a church which is located at the fortress. From here we just walk to the giant fortress. There isn’t much to see except a small hill which is the remains of the ancient dirt wall around the fortress. There is also a small museum but it was closed due to the current restrictions when we went.
There isn’t much to see but if you go you should walk to the center of the ring just to get a feel for how big this area actually used to be. If you got a chance you can visit Fyrkat or Trelleborg which has a more complete wall around them and a small museum explaining more about the Viking fortress.