In the 11th century Polabian Slavs founded a settlement at the Warnow river called Roztoc (which means broadening of a river); the name Rostock is derived from that designation. The Danish king Valdemar I set the town aflame in 1161.
Afterwards the place was settled by German traders. Initially there were three separate cities:
1. Altstadt (Old Town) around the Alter Markt (Old Market) with St. Petri (St. Peter's Church),
2. Mittelstadt (Middle Town) around the Neuer Markt (New Market) with St. Marien (St. Mary's Church) and
3. Neustadt (New Town) around the Hopfenmarkt (Hop Market, now University Square) with St. Jakobi (St. James's Church, now demolished).
The rise of the city began with its membership of the Hanseatic League. In the 14th century it was a powerful seaport town with 12,000 inhabitants and the biggest city of Mecklenburg. Ships for cruising the Baltic Sea were constructed in Rostock. In 1419 one of the oldest universities in Northern Europe, the University of Rostock, was founded.
At the end of the 15th century the dukes of Mecklenburg succeeded in enforcing their rule over the town of Rostock, which had until then been only nominally subject to their rule and essentially independent. They took advantage of a riot known as Domfehde, a failed uprising of the impoverished population. Subsequent quarrels with the dukes and persistent plundering led ultimately to a loss of economic and political power.
In 1565 there were further clashes with Schwerin that which had far-reaching consequences. Among other things, was the introduction of a beer excise that favoured the dukes. John Albert I advanced on the city with 500 horsemen, after Rostock had refused to take the formal oath of allegiance, and had the city wall slighted in order to have a fortress built. Not until the first Rostock Inheritance Agreement of 21 September 1573, in which the state princes
