viking fortress researchers
November 19, 2014

Archaeologists Confirm Age Of Viking Fortress

Eric Hopton for redOrbit.com - Your Universe Online

Has one of Harald Bluetooth’s fortresses come to light?

In September, redOrbit's April Flowers reported that archaeologists from the Danish Castle Centre and Aarhus University had discovered the remains of what they believed to be a Viking fortress.

Named Borgring, the castle lay in a field belonging to Vallø Manor, located west of Køge on the east coast of Sealand. This was the first time in over 60 years that such a fortress had been unearthed in Denmark. Since that time, archaeologists have been working hard to date the fortress accurately and prove its Viking status.

The wait is over. “Now we know without doubt that we have found a fortress from the 10th century,” said archaeologist Nanna Holm, curator of the Danish Castle Centre, in a recent statement.

When the original discovery was announced, the team responsible for the dig was sure in their own minds that they had found a Viking ring fortress. Not everyone was convinced, and many archaeologists have argued the point online. But now, the results of two carbon-14 dating tests have settled those arguments once and for all.

The carbon dating was performed by the AMS 14C Dating Centre in the Department of Physics and Astronomy at Aarhus University, in collaboration with Accium BioSciences laboratories in Seattle.

Marie Kanstrup, an employee at the AMS 14C Dating Centre, said in a statement: “The two samples were both taken from the outermost tree rings of charred logs that were found in the northern gateway of the fortress. The results of the two samples are almost identical: The fortress was built in the period between the year 900 and the beginning of the 11th century.”

Image Above: 3D reconstruction of the northern gateway of the Viking fortress Borgring, Denmark. The reconstruction is produced by Archaeological IT for the Borgring project. The reconstruction is based on excavations and surveys conducted by Aarhus University and The Museum of South East Denmark in 2014. © Peter Jensen Archaeological IT, Aarhus University.

Søren Sindbæk, a professor of medieval archaeology at Aarhus, said that the archaeologists are still trying to establish a more precise date for the fortress. This would be an important step towards understanding the role of the fortress in the Viking age. “We would like to determine a specific year” said Sindbæk. “The carbon-14 method can’t provide that, but we are working on different methods that can help us date the fortress even more precisely.”

So is this the home of Harald Bluetooth, as some have claimed? Sindbæk is not entirely convinced yet but said they have dated it to the 10th century and, as he puts it, “the trail is getting hotter. The things we’ve discovered about the fortress during the excavations all point in the same direction. We already know that there’s a good chance that we’ll find conclusive evidence next year.” Excavations have closed for this year but work will continue in 2015.

There is some controversy over the derivation of Harald's nickname. The “Bluetooth” was first documented in the “Chronicon Roskildense” in 1140. One explanation is that Harald might have had a discolored, or “blue” bad tooth. Another possible explanation is that Harald liked to wear blue – the most expensive color, which underlined his royal status.

The archaeologists’ now know that the Viking fortress was built right next to the open sea. “The excavation showed that there was a basin of fresh or brackish water right next to one side of the fortress – presumably a quite narrow inlet leading out to Køge Bay. When the fortress was built, hundreds of tons of the heavy clay subsoil would have had to have been dug out into the sea basin,” said Nanna Holm, curator and archaeologist at the Danish Castle Centre. Holm believes this work would have been carried out to give the fortress an impressive location and to symbolize power.

The construction of the fortress is very similar to other Viking fortresses such as Fyrkat near Hobro, Aggersborg near the Limfjord, and Trelleborg near Slagelse. Archaeologists know that these fortresses definitely date from the reign of Harald Bluetooth and Borgring appears to be part of the same building program.

Søren Sindbæk explained that “There are a lot of similar details in these structures. And it’s been wonderful to see the same things coming to light at Borgring. In addition to the structure of the rampart and the gates, we have also found traces of a street with wood paving running along the inside of the rampart – just like in Fyrkat, Aggersborg and Trelleborg. The most striking thing, however, is the measurements of the fortress. The rampart of Borgring is 10.6 meters wide. That is exactly the same width as the rampart of Fyrkat. So it’s hard to avoid the sense that the same master builder was responsible.”

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