Vesthimmerlands Museum has announced plans for a new visitor center to cater to visitors at the circle fortress of Aggersborg, believed to be Harald Bluetooth's largest fort. 

The news comes one year after Aggersborg was named a World Heritage Site, together with four more Viking Age circular forts in Denmark. 

Growing popularity 

UNESCO awarded World Heritage status to the five Viking Age circular fortresses in 2023. 

Though the original wooden buildings have long since disappeared from view, archeologists have been able to uncover evidence of their underlying structure at the sites of Aggersborg, Fyrkat, Nonnebakken, Trelleborg, and Borgring. 

The fortresses, which were built in the 10th century, were positioned near important land and sea routes across the Jutland peninsula and on the islands of Funen and Zealand. 

According to a recent article in the Danish news portal DR, each location has seen a noticeable rise in the number of visitors since UNESCO granted the award. 

However, while the sites at Fyrkat and Trelleborg already have visitor centers, Aggersborg does not currently have any special facilities. 

To provide visitors with a more rounded experience, the Vesthimmerlands Museum has drawn up new plans for the Aggersborg site. The museum initially intends to construct a welcome pavilion, an interactive exhibit, and an activity area for families at the site. 

It will also add steps and ramps on the earthen rampart to improve access and provide guided tours for visitors. 

In the long term, the museum intends to build a larger visitor center that will tell the story of how Harald Bluetooth consolidated his power in the Limfjord region. 

A Viking house has been reconstructed at the Fyrkat fortress near Hobro, Denmark, complementing the Viking Center Fyrkat built in 1993, while Aggersborg, the largest fortress, still lacks amenities. Photo: trabantos / Shutterstock

Grand designs 

Harald Bluetooth reigned as the king of Denmark from around 958 to 987, playing a key role in establishing the Jelling Dynasty and also ruling Norway for several years. 

Bluetooth, father of Sweyn Forkbeard and grandfather of Cnut the Great, was one of the most powerful leaders of the Viking Age and played a crucial role in introducing Christianity to Denmark. 

There is some debate as to why Bluetooth built the five fortresses, which appear to have only been in operation for approximately ten years. 

While some historians believe they were constructed to serve as a bulwark against potential invasions from Norway and Sweden, others argue they were meant to protect Denmark against the threat of the Holy Roman Empire from the south. 

In its decision to award World Heritage status to the site, UNESCO noted that Bluetooth's ability to organize such a large-scale project represented a significant step in Scandinavia as the region transitioned from smaller and disparate kingdoms and fiefdoms to a collection of nation-states. 

Denmark is home to five confirmed Viking ring fortresses, constructed around 980, with Trelleborg being the first discovered and featuring the clearest visible geometry. Photo: Thue C. Leibrandt (CC BY-SA 3.0)

The greatest of all 

The first fort to be discovered was Trelleborg in 1936. In fact, the circular fortresses are often known collectively as trelleborgs

In the ensuing decades, more structures were revealed, with the last of them, Borgring, only found in 2014. 

The five fortresses share the same distinctive circular shape and are believed to have each consisted of fortified wooden ramparts with four separate gateways. 

Aggersborg was first excavated in 1945 by the National Museum of Denmark, and several further digs have taken place since then. 

With an internal diameter of 240 meters, it is the largest of the circular fortresses and has yielded more than 30,000 artifacts.

The scale of Aggersborg is truly impressive. It is believed that the fortress could have held a garrison of 5,000 soldiers and up to 48 longhouses, arranged geometrically in the four quadrants of the fortified ring. 

It is estimated that constructing the structure required 5,000 oak trees and took several years to complete. 

While Denmark boasts five original Viking ring fortresses, the Trelleborgen in Trelleborg, Sweden, features a large reconstruction of a Viking Age ring fortress. Photo: Danita Delimont / Shutterstock

Serving international interest 

Today, the site at Trelleborg is a major tourist attraction, with a Viking village and a recreated fortress, while Fyrkat also has an adjacent museum and some reconstructed Viking Age buildings. 

Although the other three sites do not yet have significant permanent facilities, a center at Borgring is scheduled to open in 2025. 

As the largest of the fortresses, Aggersborg naturally has enormous potential as a site of tourism and historical education. 

Speaking to DR, the museum director Broder Berg noted, "A place on the World Heritage List is a mark of authenticity. When something is on the list, it means it is vital to mankind and attracts guests from far and wide." 

"We have even received an inquiry from a person in Kuala Lumpur who asked about Aggersborg's opening hours. We feel that we have gained a different status, and interest will only increase in the coming years." 

We get to provide readers with original coverage thanks to our loyal supporters. Do you enjoy our work? You can become a PATRON here or via our Patreon page. You'll get access to exclusive content and early access.

Do you have a tip that you would like to share with The Viking Herald?
Feel free to reach out to discuss potential stories that may be in the public interest. You can reach us via email at with the understanding that the information you provide might be used in our reporting and stories.