Offa's Dyke, a massive linear earthwork, roughly followed by some of the current border between England and Wales, is in places up to sixty-five feet (nineteen point eight meters) wide (including its flanking ditch) and eight feet (two point four meters) high, forms some kind of delineation between the Anglian kingdom of Mercia and the Welsh Kingdom of Powys.
Much of the earthwork can be attributed to Offa, King of Mercia from 757 to 796.
Its structure is not that of a mutual boundary between the Mercians on the one side and the people of Powys on the other.
The earthwork was dug with the displaced soil piled into a bank on the Mercian (eastern) side.
Where the earthwork encounters hills, it passes to the west of them, constantly providing an open view from Mercia into Wales.
The dyke may have been constructed as a defensive earthwork, as well as a political statement of power and intent.
It extends about one hundred and twenty miles (one hundred and ninety-five kilometers) through the Welsh marches from the Bristol Channel in the south to the Dee estuary in the north.
