Poznan Cathedral is located on "Cathedral Island” which is an island between two branches of the river Warta. Poznań Cathedral and other ecclesiastical buildings occupy the central part of the island. Cathedral Island is part of the city's former Nowe Miasto ("New Town") district, although it is actually the oldest part of the city, where the rulers of the early Polish state in the 10th century had one of their palaces.
The cathedral was originally built in the second half of the 10th century within the fortified settlement on Cathedral Island. This was one of the main political centers in the early Polish state, and included a ducal palace (excavated by archaeologists since 1999, beneath the Church of the Virgin Mary which stands in front of the cathedral). The palace included a chapel, perhaps built for Dobrawa, Christian wife of Poland's first historical ruler, Mieszko I. Mieszko himself was baptized in 966, possibly at Poznań – this is regarded as a key event in the Christianization of Poland and consolidation of the state. The cathedral was built around this time; it was raised to the status of a cathedral in 968 when the first missionary bishop, Bishop Jordan, came to Poland.