I was recently in the Łagiewniki Sanctuary in Krakow where before 1938 Saint Sister Faustyna was having visions of Jesus and she wrote a dairy which you can read and download here:
Jesus said to her that whoever will pray a prayer called
THE CHAPLET OF THE DIVINE MERCY
once in the life then his soul will meet his mercy.
Jesus said to her also under her direction to paint a painting of him
Although it is neither the first picture painted under Sister Faustina’s direction nor the first image displayed in the chapels of her Congregation, Jesus’s will: I desire that this image be venerated, first in your chapel, and [then] throughout the world (Diary 47) has been fulfilled by means of this picture.
and here you can send a prayer online to this place and it will be read and prayed on mass
|This road lead to another Chapel where is The picture of the Merciful Jesus and Saint Sister Faustyna grave|