Founded in 1408 and absorbed by a Dominican monastery in 1501, the church was remodelled in the 18C. This fine example of the late Baroque is the main Polish church here. Inside, the Rococo interior is extremely rich: 16 altars, 45 pictures, organs virtually hidden by stuccowork and statues. The painted dome is a whirl of saints and clouds. In the labyrinthine crypt are 2 000 mummified bodies (including Napoleonic troops), some dating back to the 17C.