This characteristic church at the far end of ul. Św. Jana was completed in two stages back in the 18th century: the main body of the church was designed by Kacper Bażanka and completed in 1728, while the facade - courtesy of Eclecticist architect Francesco Placidi - was tacked on thirty years later. The inside sports Roman-inspired polychrome paintings by Franz Eckstein and Jozef Piltz. Both the church and the adjacent monastery on both sides - parts of which are occupied by the Czartoryski Museum - belong to the Piarist Order, hence the name of the street it's on. Also of note is the art gallery in the crypt underneath the main entrance to the church.