Vallum (Hadrian's Wall)

The earliest surviving mention of the earthwork is by Bede[1] who refers to a vallum, or earthen rampart, as distinct from the wall, or murus; the term is still used despite the fact that the essential element is a ditch, or fossa.

In the central sector the wall runs along the top of the crags of the Whin Sill, while the Vallum, laid out in long straight stretches, lies in the valley below to the south, as much as 700 metres (2,300 ft) away.

The Vallum was constructed a few years after the wall was completed, as it deviates to the south around the first series of forts (including Chesters) but earlier than that at Carrawburgh, datable to c. 130 by a fragmentary inscription.

Archaeologists have speculated that either the Vallum was then deemed unnecessary because economic development and pacification of the frontier district had rendered it obsolete, or that it was proving to be a hindrance to military and authorised civilian traffic.

[2] Although there is no definitive historical evidence as to why the Roman army built this unusual barrier, modern archaeological opinion is that the Vallum established the southern boundary of an exclusion zone bounded on the north by the wall itself.