Our Lady of Gietrzwald is Poland's only approved apparition of the Blessed Mother (aleteia.org)
On the evening of June 27, 1877, the Marian apparitions in Gietrzwald began, lasting until September 16 of the same year. The primary visionaries were Justyna Szafryńska, 13, and Barbara Samulowska, 12. These are the only Marian apparitions in Poland recognized by the Catholic Church.
The apparitions in Gietrzwald were officially recognized by the Catholic Church on September 11, 1977, exactly one hundred years later. This approval followed the IV National Mariological Congress and the centennial celebrations of the apparitions, led by Cardinal Karol Wojtyła, the then Archbishop of Krakow. The formal document was signed by Bishop Józef Drzazga of Warmia, making Gietrzwałd the only officially recognized Marian apparition site in Poland and one of twelve worldwide.