Libraries are physical repositories of texts, and they are also mental constructions concerning knowledge and memory. In The Decline and Fall of the Roman Empire (1776-1788), Edward Gibbon alludes to a number of famous libraries in antiquity. Often he recognizes in them a Renaissance and Enlightenment project to promote communication and the increase of knowledge, a project to which a bulky learned construction like the Decline was necessarily committed. But the historian is also remarkably sensitive to the ways in which the accumulation of memory is dangerous and perhaps even a fiction. More than once, the narration of the destruction of a library ends up casting doubt on its very existence. This skeptical view of the architecture and project of learning is related to Gibbon's vision of empire, and it is interesting too for his understanding of East and West: the libraries of Alexandria and Constantinople, his key examples, are at the borderlines of different civilizations.