The Viking name for Aarhus was Aros, which means “the city by the river’s mouth”, and it was both a trading center and a royal navy base.
Aros was vulnerable, lying unprotected on the coastline, so the Vikings erected an elaborate defense system that included the whole bay of Aarhus.
On Helgenæs and Samsø, an outer defense-system of navybases was build, and a system of beacons was organized so that no enemy could enter the bay without the beacon-fires were lit, and the fortress of Aros was alarmed. But the real secret of the Aros Viking fortress lies hidden behind the city center.
The royal fleet didn’t dock in the ocean in front of the city but sailed up through the river, deep inside the land, until it came to the lake called Brabrand lake ( Brabrand sø). Here it lay hidden from the enemies but could in a short time sail out through the river mouth in order to defend the city walls. The many innovative defence-systems made Aros impregnable and no enemy dared attack the Viking stronghold, well that is at least until the Norwegian warrior-king Harold Hardraade came to the waters of Aros.
Harold Hardraade had just done the impossible and sacked the Danish capital, called Hedeby (Haitabuy). Now he headed towards the last Danish stronghold, the navy base of Aros. The beacon-guards on Helgenæs and Samsø stood ready, but at night, a heavy fog came into the bay and covered the Norwegian dragon-fleet as they entered unseen into the bay.
At sunrise Harold laid in front of the city walls and commenced his attack by sailing his dragonships up the Aros River. Right where the café’s lie today, and we all enjoy our coffee and brunch, is where the defenders of Aros pushed back the first Norwegian assault, but Harold was stubborn and landed further up the river, where Magasin is located today.
Here he attacked and pillaged a small christian suburb that lay outside the city walls, but with that dark deed, his luck ran out, and the Norwegian Vikings was pushed back into the ocean by a strong Danish shieldwall led by Svein Ulfson, the last of the Jelling-kings.