The Library of Alexandria was one of the largest and most significant libraries of the ancient world.
Why it is true
Founded in the third century BC in Egypt, it was a center of knowledge that gathered the greatest intellectuals of the time, storing hundreds of thousands of scrolls before its eventual destruction.
Source: Library
Would you rather be asked first?
This is the reading side of the site, so the answer is in the sentence above — that is the whole point of it. Test yourself works the other way round: the question comes on its own, and the fact and the explanation only appear once you have answered.