I finally took your (collective) advice and moved up to Emperor last night... played a random game. I decided to take out my only neighbor on the large island/small continent. The Arabs didn't put up much of a fight. When I took Mecca, I found that he had built the Great Library. Hooray. However, when I took over the city and went to build a University, I didn't have that option yet. I had to build a Library first. So that is my question... why is the Great Library not a Library?