Battle of the Spree
1005 CE.
Shown on the map at 52.117°, 14.117°.
The Battle of the Spree was a battle part of the German–Polish War which took place on 6 September 1005 between the Duchy of Poland and the Holy Roman Empire led by Henry II. It ended up Inconclusive.
Text from the Wikipedia article Battle of the Spree, licensed CC BY-SA 4.0.