The Archcathedral Basilica of St. Peter and St. Paul is one of the oldest churches in Poland and the oldest Polish cathedral, dating from the 10th century. It stands on the island of Ostrow Tumski. There are the tombs of the first Polish rulers, Mieszko I and Bolesław Chrobry.
The current appearance of the cathedral is from the rebuilding of the years 1948-1956 conducted under the direction of Francis Morawski.
The main entrance has a bronze door with scenes from the lives of St. Peter and St. Paul and a Latin inscription which reads PRIMA SEDES EPISCOPORUM POLONIAE (The First Seat of the Church in Poland).
In the basements there are the tombs of the first Polish rulers, Mieszko I and Bolesław Chrobry.