Conversation so far:
what was the function of the leaning tower of pisa during the world war ii
In World War II, the Allies found out that the Nazis were using the Leaning Tower of Pisa as an observation post.
was the Leaning Tower of Pisa damaged during the war
A US Army Sergeant never ordered a strike on the leaning Tower in order to preserve this piece of art and history.

Question: when was the tower completed
Self-contained rewrite: when was  the Leaning Tower of Pisa completed