With an elevation of 2,468 feet, Ceredigion, formerly known as Cardiganshire, is a Welsh county that stretches from the west coast on Cardigan Bay to inland hills and valleys and the highland of Plynlimon (752 metres). The ancient county of Cardiganshire is coterminous with Ceredigion. Aberaeron is the administrative centre of the county. Like in other parts of western Britain, the oldest evidence of ancient human occupancy in Ceredigion is on the high land, which includes many tumuli and cairns in the north and south of the county. A Roman trackway known as Sarn Helen can be found to the east. There were frequent raids on the open shore during the post-Roman years, particularly by Irish and Scandinavians. Ceredig, son of Cunedda Wledig of northern Wales, is claimed to have seized control of the Teifi’s whole basin at this time. The county of Ceredigion is named after this mythical person. Ceredigion’s steep terrain made Norman penetration difficult. There was a lengthy sequence of conflicts between the Normans, who wanted to keep the valley lines open, and the Welsh herders from the hills during the 12th and 13th centuries. In southern Ceredigion, the town of Cardigan features a Norman bridge (rebuilt in 1640) and castles dating from 1093 and 1160. Cardigan is also a historically significant county town (seat).