The Archbishopric of Gniezno held one of the largest aggregates of landed estates (latifundia) in Piast Poland (the other great landowner was the Bishop of Cracow). They spanned vast tracts of land from Kujawy through east Wielkopolska, the Lands of Łęczyca and Sieradz, Mazowsze down to Małopolska. By the end of the Middle Ages the Bishop of Gniezno possessed c. 320 villages and 14 towns. As many as nine towns were founded outside Wielkopolska, while the remaining five (Grzegorzew, Kamień, Kwieciszewo, Opatówek, and Żnin) were set up on the core territory of the province. This article focuses on the latter group, ie. town locations in Wielkopolska proper.Drawing on the available archaeological studies and extant written sources the author of this article conducts a thorough analysis of the formation of the five ecclesiastical towns of Wielkopolska from the pre-location period up to their incorporation in accordance with German law and the emergence of urban communities within clearly demarcated borders. The high point of city-founding coincided with the rule of Archbishop Janisław (1314-1341). It was then that Kwieciszewo, Grzegorzew and Opatówek were founded. It is a characteristic trait of the history of those places that prior to the incorporation in each case the neighbouring villages were clustered round a settlement which, in the course of the 15th century, was transformed into an urban centre. The urban transformation was accompanied by the construction of a parish church, municipal buildings for the estate managers, and occasionally a fortified residence (Kamień, Opatówek, Żnin). As a rule, the new towns were founded along the main routes from Wielkopolska to Gdańsk and West Prussia, Kujawy, and Małopolska.Of the five towns that had been erected by the end of the 14th century only Żnin developed into a big and vibrant urban centre that could successfully compete with more prosperous crown cities. The remaining archbishop's towns did not differ very much from villages. Agriculture rather than crafts and trade continued to be the main source of livelihood for the town-dwellers. One of the reasons of their slow growth was the adoption of the Law of Środa, a variant city charter named after Środa Ślaska, a town in Silesia. It tended to restrict the authority of municipal self-government, strengthened the role of the hereditary mayor and the town patron, and placed greater material burdens on the burghers.