Toward the mid-8th Century the Havolane established Spandow, present-day Spandau, on the banks of the Havel. Historians believe this settlement was closest to the present-day area of Berlin. Around 825 fortifications were built around Spandau and Kopenick. These two remained the only large towns in the area until the early 1000s. At the beginning of the 9th Century local Slavic tribes founded Berolina, a name mentioned in Latin chronicles, known as Berlin today. According to some sources, this name meant: a dam on a river. The small town was located on a trade route connecting the Baltic Sea with southern Europe.

In the middle of the 10th Century emperor Otto I took control over the area and its inhabitants. As a result, the Slavs became German subjects. Otto I founded the towns of Brandenburg and Havelberg. Bishops of the latter usually lived in Wittstock or Plattenburg, both several miles north of Havelberg. During the great Slavic uprising in 983 the abbeys were destroyed and the clergy and German officials were killed. The Slavic tribes in the lands east of the Elbe remained pagan for another 150 years.

In the early 12th Century, the Germans conquered the lands of present-day Brandenburg. As already mentioned, they were inhabited by the Slavs at the time, who were either driven out, or came under the rule of the invaders. However, some of the population survived. For example, the Sorbs live in the region of Lusatia (Saxony and Brandenburg states) even to this day. At that time, the fortifications offered the town folk protection from incursions.

In 1134, the Roman Emperor Lothar II granted to Albert I the Northern March – the empire's territorial organisation on the lands taken from the Wends (Hevelles). Albert I was a duke of Saxony and a margrave of Brandenburg in the mid-12th Century. Until the 1400s, a part of the future Brandenburg territory was occupied by the Wends. Their descendants still make up a large part of the current population of this area. In 1150, Albert officially inherited Berlin from Pribislav, the last king of the Hevelles who passed away that year. Christianity began to influence these lands, and German and Slavic tribes intermarried.