The abbey church is thought to be one of the first brick buildings erected in Poland. Though rebuilt in the 18th century, it's preserved much of its original Romanesque shape and boasts two original portals. The one next to the main entrance, partly hidden behind the baroque tower (1780s), is particularly fine; on the tympanum (1220s), you can make out King David on his throne playing the harp to Queen Bathsheba.
The church’s showpiece is St Hedwig’s Chapel (Kaplica Św Jadwigi), to the right of the chancel.
The chapel was built soon after the canonisation of the princess, and the graceful, ribbed Gothic vaulting has been preserved unchanged. Its central feature is the saint’s Gothic sarcophagus, an elaborate work in black marble and alabaster created in stages between 1680 and 1750. To the left of the tomb is the entrance to the three-nave crypt, the oldest part of the church.
The rest of the chapel is full of gilded and marbled altars; in the nave are 18 scenes from the saint’s life. The beautiful black organ is striking against the white walls and pastel colours of the ornamentation.