Offa’s Dyke (Welsh: Clawdd Offa) is a large linear earthwork that roughly follows the current border between England and Wales. The structure is named after Offa, the 8th century king of Mercia, who is traditionally believed to have ordered its construction. Although its precise original purpose is debated, it delineated the border between Anglian Mercia and the Welsh kingdom of Powys.
The original Dyke crossed low ground, hills and rivers. Much of its route is followed by the Offa’s Dyke Path; a 177 mile (283 km) long-distance footpath that runs between Prestatyn, Liverpool Bay in the north and Chepstow, Severn Estuary in the south.