Vast quantities of Roman documents survived the empire. Much of this material was lost to barbarian depredations, but quite a lot was preserved. The Romans used papyrus and parchment --thin animal skins-- as paper. Sources of papyrus dried up with the fall of Rome, and knowledge of parchment was also lost during the Dark Ages, only to be re-discovered later. This made old Roman documents valuable for their paper. Medieval scribes would remove the Roman writing and reuse the paper. As a result, monks often collected old Roman documents, and they early developed the habit of preserving ancient literature and knowledge. While the principal function of the monasteries and their scholarly monks was the preservation and growth of Christian writings, they could read the Latin on the old Roman documents (before the texts were removed to be replaced by religious material). The monks took notes, and much of what we know about Rome comes from this monkish curiosity and note taking.