Newly-discovered ancient fortress reveals architectural accomplishments of Vikings

Archaeologists in Denmark have discovered a ring-shaped Viking fortress on the Danish island of Zealand, which historians believe may have been used to train warriors before launching an invasion of England. While the Vikings carry a reputation as brutish invaders, the latest finding shows that they were also accomplished builders.

"The Vikings have a reputation as [fierce Norse warriors] and pirates. It comes as a surprise to many that they were also capable of building magnificent fortresses," Søren Sindbæk, a professor of medieval archaeology at Aarhus University in Denmark, said in a statement.

According to a report in Live Science, the newly-discovered fortress, which is believed to date back to the 10^th century, is the third-largest Viking ring fortress discovered and the first time a circular battlement has been uncovered in more than sixty years. While other Viking fortresses have been found before, the ring-shaped constructions, which are known as Trelleborg fortresses, are rare and unique to Denmark.

So far, only small areas of the new fortress have been uncovered, but findings so far show that it is consistent with others that have been found, and sticks to a strict geometric pattern consisting of a circular wall with a 145-metre diameter, a 10-metre wide circular rampart surrounded by a palisade of wooden spikes, four gates facing outward in different compass directions, and an interior courtyard symmetrically divided into four quarters. It is believed that Viking longhouses would have been constructed inside the fortress.

"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," said Nanna Holm, curator of the Danish Castle Centre in Denmark, who helped identify the site of the newly unearthed fortress.

A reconstruction of what the ring fortress would have looked like. Image: Jørgen Falck

Three other Viking ring fortresses have been found in Denmark to date, but archaeologists long suspected that a fourth Trelleborg fortress might exist on the island of Zealand. The area known as Vallø, on the east coast of the island, would have been an ideal location for such a structure as it overlooked the Køge river valley, which at that time was a navigable fjord and one of the best natural harbours on the island.

The team of archaeologists therefore used advanced laser and magnetic tools to search for the remains of such a structure. "By measuring small variation[s] in the Earth's magnetism, we can identify old pits or features without destroying anything," Sindbæk said. "In this way, we achieved an amazingly detailed 'ghost image' of the fortress in a few days. Then we knew exactly where we had to put in excavation trenches to get as much information as possible about the mysterious fortress."

A scan showing the location of the newly-discovered fortress. Image source.

The research team believes the fortress dates back to the reign of Harald Bluetooth, a 10^th century king who Christianised Denmark and Norway.

"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," said Holm. "If we can establish exactly when the fortress was built, we may be able to understand the historic events which the fortress was part of."
Featured image: A Viking 'ring fortress' at Trelleborg in western Zealand Photo: Thue C. Leibrandt/Wikimedia Commons

By April Holloway-