I’ve been to Poland. In Warsaw I saw All Saints’ Church with the statue of Pope JPII, the Warsaw Ghetto memorial and museum (also you can see part of the Ghetto wall which is left standing), and the grave of Blessed Jerzy Popieluszko (A giant Rosary) at St. Stanislaus Kostka Church, the basement of which is also full of interesting murals of the Crusades and St. Francis and such, painted by young children. There is a 9/11 memorial at the St. Stanislaus Kostka church, part of the Twin Tower beams made into a cross.
Pope JPII’s hometown with the church where he worshipped as a child is also very nice. He lived literally across the street from the church. Be sure to have some of his favorite dessert when you visit that town, it’s a sort of cream cake. The Divine Mercy shrine is very big and not centrally located, so plan on spending at least a half day there if you want to see it properly. In Krakow’s historic area are some nice churches that have adoration every day so be sure to stop in. Also the market at Krakow is a great place to shop for souvenirs, the prices are very reasonable, and you can hear the trumpeter at certain times from the tower of the historic church, also tour the beautiful church.
Unfortunately I was not able to get out to the St. Maximilian Kolbe shrine as we were only in Poland for a couple of days, so that’s on my list for a future trip. You have to take a train from Warsaw to get there. I did get to see the cell where he died at Auschwitz. You are not allowed to go into the cell, just look in. I reached through the bars when guard was not looking and touched a holy card of St. Maximilian to the wall.
I also understand that if you want to go to Mass in Poland on your own and it’s not an arranged Mass for a tour group, then you should arrive early because the Masses are so full you cannot get a seat otherwise.