We do not know when the Gaels first entered Ireland, coming according to ancient Irish legends across the Gaulish sea. One invasion followed another, and an old Irish tract gives the definite Gaelic monarchy as beginning in the fourth century B.C. They drove the earlier peoples, the Iberians, from the stupendous stone forts and earthen entrenchments that guarded cliffs and mountain passes. The name of Erin recalls the ancient inhabitants, who lived on under the new rulers, more in number than their conquerors. The Gaels gave their language and their organisation to the country, while many customs and traditions of the older race lingered on and penetrated the new people. Over a thousand years of undisturbed life lay before the Gaels, from about 300 B.C. to 800 A.D. The Roman Empire which overran Great Britain left Ireland outside it. The barbarians who swept over the provinces of the empire and reached to the great Roman Wall never crossed the Irish Sea. Out of the grouping of the tribes there emerged a division of the island into districts made up of many peoples. Each of the provinces later known as Ulster, Leinster, Munster and Connacht had its stretch of seaboard and harbours, its lakes and rivers for fishing, its mountain strongholds, its hill pastures, and its share of the rich central plain, where the cattle from the mountains "used to go in their running crowds to the smooth plains of the province, towards their sheds and their full cattle-fields." All met in the middle of the island, at the Hill of Usnech, where the Stone of Division still stands. There the high-king held his court, as the chief lord in the confederation of the many states. The rich lands of Meath were the high-king's domain.