Celtic mythology is the body of myths belonging to the Celtic peoples. Like other Iron Age Europeans, Celtic peoples followed a polytheistic religion, having many gods and goddesses. The mythologies of continental Celtic peoples, such as the Gauls and Celtiberians, did not survive their conquest by the Roman Empire, the loss of their Celtic languages and their subsequent conversion to Christianity. Only remnants are found in Greco-Roman sources and archaeology. Most surviving Celtic mythology belongs to the Insular Celtic peoples (the Gaels of Ireland and Scotland; the Celtic Britons of western Britain and Brittany). They preserved some of their myths in oral lore, which were eventually written down by Christian scribes in the Middle Ages. Irish mythology has the largest written body of myths, followed by Welsh mythology.