Monument in Poznań, Poland.

 Crosses in Poznań commemorating the 1956 protests and subsequent Polish protests against the Communist political system. 

This photo shows the monument from a different angle: http://en.wikipedia.org/wiki/File:Poznański_Czerwiec_reforma_RB1.JPG

http://en.wikipedia.org/wiki/Poznań_1956_protests

http://en.wikipedia.org/wiki/History_of_Poznań

Interesting stamps!