Today Poland celebrates its Independence Day 101 years after WWI ended, marking the resumption of Polish sovereignty.
November 11th was chosen specifically to mark the day in 1918 that Józef Piłsudski returned to Warsaw from German imprisonment to be granted control of Polish military forces, effectively taking leadership of a newly independent country: the Second Polish Republic, which ended 123 years of partition between Russia, Prussia, and Austria and lasted until the takeover of Poland during the next World War by Nazi Germany and the USSR.
For most Poles, Independence Day means remembering this history with pride, or at least getting a day off work. However, it has also given rise in recent history to sometimes violent ultra-nationalist marches, especially in the capital Warsaw. (Traditionally Krakow has been relatively safe, but revelers are advised to be on guard.)
The official events in Poland today will be a 10:00 Catholic mass at Wawel Cathedral, followed by a military parade at 11:40 from there to Plac Matejki. Beginning at 15:00, people will gather to sing patriotic songs on the Main Square from a free song book which will be distributed.
Also, flowers will be laid at Auschwitz in front of a wall used for the Nazi execution of Jews, Roma, LGBTQ people, Polish political prisoners, and others by the Germans during WWII.