National 3rd of May Holiday

On May 3rd, 1791, the Constitution of the Polish-Lithuanian Commonwealth was adopted. It was modern Europe's first codified national constitution and the second in the world, following the American one. 

Jan Matejko, Constitution of 3 May, 1791, 1891

Foreground: King Stanisław August (left) enters St John's Collegiate Church where deputies will swear to uphold the Constitution. Background: the Royal Castle where the Constitution has just been adopted. 

(more about the painting here)