A Viking fortress discovered in Denmark in September, 2014 could have once belonged to King Harald Bluetooth, according to carbon dating results.

Archaeologists believe that the castle is similar enough to other buildings owned by Bluetooth to suggest that this new fortress also belonged to him. Now that carbon dating places it from the 10th century, evidence of Bluetooth as the castle's owner is growing.

Archaeologists took two samples from tree rings of logs found in one of the gateways of the fortress. The carbon-14 results confirmed that both samples came from between the year 900 and the end of the 10th century.

After excavation, archaeologists discovered that one side of the fortress was standing next to water, suggesting that the fortress sat next to an 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," says archaeologist Nanna Holm. "When the fortress was built, hundreds of tonnes of the heavy clay subsoil would have had to have been dug out into the sea basin."

The only reason for such a location? Archaeologists believe that the fortress symbolized power, perhaps built for a king like Bluetooth.

The excavation also showed that the fortress was similar to other fortresses previously discovered, such as Fyrkat, Aggersborg and Trelleborg, all built during the time of Bluetooth.

Harald Bluetooth ruled as king of Denmark and Norway in the first century. He is known mostly as the King that united Denmark and conquered Norway. During his reign, he directed reconstruction of many public works, including the oldest known bridge in southern Scandinavia. He also oversaw the construction of ring forts. These fortresses had similar designs, including circular gates and courtyards divided into four areas.

In this newly discovered fortress, archaeologists also found evidence of a wood paved street inside the rampart, just like what was found at the other three locations.

"The most striking thing, however, is the measurements of the fortress," says Sindbæk.

"The rampart of Borgring is 10.6 metres 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."

However, to tie this new fortress to Bluetooth, more accurate dating is needed. Knowing exactly when construction of the fortress took place is important in knowing where it stands in Viking history.

Archaeologists expect answers sometime next year.

[Photo Credit: Aarhus University]