Eat Pierogi (PS: May contain pork, for some morroccans this is an issue). Some of them are very very tasty, specially one that have a sauce made with fried meat, it is wonderful.
Drink Vodka (Zubrowka, Belvedere, Chopin, all those worldwide famous treasures inside bottles came from there).
Visit Old towns (I Visited the ones of Poznan and Krakow, they are impressive).
For a not happy, but a valuable and shocking human experience, visit Auschwitz near Krakow and the Warsaw Uprising Museum in Warsaw.
If you like skiing, people recomend the Tatars in the south. I never went but in January i will go to Wisla :)
Do not feed the pidgeons.