Trelleborg fortress

One of the Trelleborg fortresses, via kultutrarv.dk

South of Copenhagen, on the island of Zealand, archaeologists have done something they haven’t done for over 60 years: discover a new Viking fortress, and a massive one at that.

Measuring 145m from side to side, this is not just any Viking fortress, but one of the perfectly circular Trelleborg fortresses built during the reign of King Harald Bluetooth.

The Viking Age was characterised by widespread upheavals in Denmark and the entire Nordic region. One of the most impressive testimonies to this era are the six so-called Trelleborg fortresses, including Nonnebakken, Fyrkat, Aggersborg and the flagship Trelleborg.

Built by King Harald Bluetooth who reigned in Denmark from 958 AD to 986 AD, the fortresses all conform to the same rigorous geometric plan – perfectly circular ramparts with gates opening to the four corners of the earth and divided into quarters, each containing four longhouses.

Although six had previously been found, archaeologists had suspected there was another and this recent discovery seems to have proven them right. “Our investigations show that the new fortress was perfectly circular and had sturdy timber along the front; we have so far examined two gates, and they agree exactly with the ‘Trelleborg’ plan. It is a marvelous find” said Nanna Holm, curator at The Danish Castle Centre, of the recent discovery – the seventh of its kind.

Burnt postsBurned to the ground

Perhaps the most remarkable thing about this newly discovered Trelleborg-style fortress, however, is the clear evidence that this fearsome military installation had been attacked.

“The gates were burned-down; in the north gate we found massive, charred oak posts” said Holm.

For many, it may come as a surprise that Vikings even built fortresses. After all, weren’t they the ones that everyone else built fortresses to defend themselves against?

Søren Sindbæk, professor of medieval archeology at Aarhus University, explains: “The Vikings have a reputation as berserkers and pirates [but] they were also capable of building magnificent fortresses”

Denmark’s missing Viking fortress

The team had suspected that there had been a ‘missing’ fortress in the island Zealand, explained Sindbæk. “The location at Vallø was quite the right setting in the landscape: in a place where the old main roads met and reached out to Køge river valley, in the Viking Age was a navigable fjord and one of Zealand’s best natural harbors. From there we worked our way forward step by step” he said.

The team carried out a non-invasive survey, first using new, precise laser measurements of the landscape, which revealed a almost invisible rise in the field with a clear circular outline.

The team then called in Helen Goodchild, an expert in archaeological geophysics from the University of York, England, who measured small variations in the earth’s magnetism to identify features and build a detailed ‘ghost image’ of the fortress in a few days, which the team then used to position the excavation trenches to get as much information as possible about the mysterious fortress.”

King Harald Bluetooth and the Trelleborg Plan

aerial fortressNow immortalised as a piece of wireless communications technology*, King Harald Bluetooth reigned from 958 AD until he died in 986 AD.

Unlike his father, Gorm the Old who had been buried according to Pagan traditions, Harald converted to Christianity around 960 AD.

He later had both his mother and father reburied and erected the Jelling Stone, one of the most impressive runic stones in Denmark and which contains Christian inscriptions, in their honour.

He is perhaps best known for temporarily subjugating Norway, until he in turn submitted to a renegade Swedish prince by handing over his daughter, a fleet and promising to support his attempts to claim the Swedish throne.

The site may prove to be an important discovery in the Viking history of Denmark, said Holm. “We are eager to establish if the castle will turn out to be from the time of King Harald Bluetooth, like the previously known fortresses, or perhaps a former king’s work. As a military fortification from the Viking Age, the monument may help to unravel the position of Zealand in relation to the oldest Danish kingdom”

The question remains…

So far, only small parts of the fortress have been excavated and the list of unresolved issues is long. “This is really exciting” says Søren Sindbæk. “A find like this does not happen many times in a life-time. The excavation has confirmed far more than we dared hope, but there is much more to learn.

The next big question is whether there were large buildings inside the castle, as in the known Trelleborg fortresses. The find also raises the question as to whether there will be more new Viking fortresses to discover. The exploration will be a wonderful journey of discovery”.

Clearly, the discovery of this new Viking fortress is a unique opportunity to gain new knowledge about Viking war and conflicts, but the question remains: who was brave enough to burn it down?

Source: Photos and information provided by Aarhus University and The Danish Castle Centre

*Apparently the name Bluetooth was chosen because the aim was to unify computers and mobile phones, *just like* Harald ‘unified’ Denmark and Norway.

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Maiya Pina-Dacier

Head of Community at DigVentures, Maiya digs with a trowel in one hand, and a Twitter feed in the other. She reports on all our discoveries live from the trenches, and keeps our Site Hut full of the latest archaeology news. Got a story? Just drop her a line...

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