The archdiocese basilica of the Holy Apostles Peter and Paul is the city's oldest historical monument. Its origins date back to 968, when the Poznań diocese was created. In 1962 Pope John XXIII bestowed on the temple the title of lesser patriarchal church.
Construction of the first cathedral - a three - nave pre - Romanesque basilica - was started by Prince Mieszko I around the year 968. It was many times destroyed and restored.
Today the cathedral is a three - nave basilica, with an ambulatory around the chancel. There are 12 chapels and 2 sacristies adjacent to the side naves and the ambulatory. The temple is 81 metres long and 43.5 metres wide. The main nave is 24.5 metres high, the spires are ca. 62 metres high and the small spires over the ambulatory each have 44 metres. The facade has a pointed offset portal made of profiled, glazed bricks. The bronze door in the portal depicting scenes from the lives of St Peter (on the outside) and St Paul (inside) was made in 1979. It was designed by Kazimierz Bieńkowski. Over the portal there is a high Gothic window with a rosette and above it a staircase Gothic gable with blank windows. The Baroque domes of the spires were renovated in 1952. After WWII the inside of the cathedral was restored to its Gothic form.
The cathedral is home to many precious works of art. The high altar in late Gothic style dating from 1512 came from Góra in Lower Silesia. It is a polyptychal reredo, with a pair of swinging doors on each side. Inside are the statues of Mother of God with the Infant, St Barbara and St Catherine. In the four panels of the outside wings are the statues of 12 saintly women. Over the altar there is a late Baroque crucifix and Baroque statues of Mother of God and St John. The late Gothic choir stalls dating from the beginnings of the 17th century were brought here from Zgorzelec; the late Baroque pulpit and baptismal font from 1720 came from a former Evangelical church in Milcz. On the pillar behind the archbishop's chair hangs a valuable Flemish tapestry from the first half of the 17th century.
There are many valuable works of art in the chapels. The Golden Chapel was designed by Franciszek Maria Lanci and built between 1835-41 (making use of existing walls) as a mausoleum of Mieszko I and Boleslaw the Mighty (the first rulers of Polish State).
The cathedral was the stage for many historical events, including the funerals of medieval kings and princes (the church is the oldest necropolis of the Piast dynasty rulers).
Remnants of the oldest structure of the cathedral can be found in the crypt under the aisle bay. Apart from the earliest tombs of Mieszko I and Boleslaw the Mighty, almost half of a limestone baptismal font measuring around 5 metres across is preserved. It is thought that the font is part of a baptistery build in the times of Mieszko I, before the first cathedral was erected. (It is generally assumed that it was in this part of Poznań, on the island of Ostrów Tumski, that Mieszko I accepted baptism.) You can also see there fragments of the walls that formed part of the first two cathedrals, the pre - Romanesque and the Romanesque one.