Vallum

A Roman defensive rampart of an earthworks, made as a defense obstacle around a camp or fort. It is also the name of the flat-bottomed ditch with two parallel walls running south of Hadrian's Wall in northern Britain.

[Latin ‘rampart’]. Properly, a heaped rampart of earth as, for instance, around Roman military camps, towns and regional fortifications. These were often topped with stakes. The early English historian Bede (673-735) also used the term, as is sometimes done today, to describe the whole ‘assemblage’ of two ramparts and ditch which back Hadrian’s Wall.