The Archbishopric Museum is housed in the former Lubranski Academy on Ostrow Tumski, the second-oldest higher school in Poland after Krakow's. Its collection focuses on church art, mostly from the Poznan region, and adds depth to a visit to the cathedral island.
It is not a large museum, but it is a good stop if you are interested in sacred art, early Polish history, or the church institutions that shaped this part of the city.