Viking-Age Ring Fortresses, Denmark

In most cases, they were equipped with a concentric ditch, axial streets encircled by a ring street, and rows of longhouses geometrically arranged in the four quadrants of the ring. The ring street provided access to the ramparts while the axial streets lead to the four gates.

The largest and most northerly of the ring fortresses, Aggersborg was located on a prominent rise next to a waterway that was the key military and trade route between western Europe and the Baltic, one of the most important navigation routes in Northern Europe at the time. 

Fyrkat fortress, located near the present town of Hobro in Northern Jutland, was situated on a promontory overlooking the valley of the Onsild Å river. Built in 975 CE, the fortress functioned for about five to fifteen years before being destroyed by fire. 

The fortress at Nonnebakken was built on a promontory on Funen island, with a river and marshes nearby. It was constructed next to the Viking-Age settlement of Odense which, after 900 CE, slowly developed to become a town that is now the third largest city in Denmark.

The spectacular Trelleborg shield was uncovered in 2008, during archaeological excavations in a bog immediately outside the fortress. This is the only site in Denmark to have yielded a complete Viking warrior’s shield. Made of pine wood, it measures 90 cm in diameter.

Borgring fortress on Zealand island was situated on a slope overlooking the Køge Å river. It is believed that its purpose was to protect land-based traffic. The fortress had no ditch, but was surrounded by a brook and waterlogged depressions that probably played a similar role.

While in use for only a brief period, perhaps around 30 years, this chain of Viking-Age fortresses illustrates the centralisation and securing of power by the Danish Jelling Dynasty and the consolidation of the kingdom of Denmark under King Harald.

As one of the great building projects of King Harald, these fortresses signify nobility, kingship and authority, and demonstrate his ability to command and utilise great resources during a key transition period in Northern Europe that included the conversion to Christianity.

This group of outstanding monumental military works is without parallel in Scandinavia, and is exceptional within the wider European Early Medieval context.

Shared characteristics of the fortresses include a monumental appearance, precise geometrical and symmetrical layouts, a circular shape enclosing a symbol of a cross, and similarity in construction.