Offa’s Dyke (Welsh: Clawdd Offa) is a massive linear earthwork, roughly following some of the current border between England and Wales. In places, it is up to 65 feet (20 m) wide (including its flanking ditch) and 8 feet (2.5 m) high. In the 8th century it formed some kind of delineation between the Anglian kingdom of Mercia and the Welsh kingdom of Powys. It has been the subject of considerable research in recent years, dispelling many of the earlier understandings.