Anonymous
You're probably thinking of the great library in Alexandria that was burned by Crusaders. It didn't set humankind that far back, but it was indeed a major - and pointless- loss.
Anonymous
The Library of Alexandria, which was located in the city of Alexandria in Egypt.
staisil
Library of Alexandria
The library was created by Ptolemy I Soter, who was the successor of Alexander the Great.
Historians cannot agree on the cause of the fire.
http://www.ask-aladdin.com/Alex-Travel-Information/library_of_Alexandria.html