Vallum

A term applied either to the whole or a portion of the fortifications of a Roman camp. It is derived from vallus (a stake), and properly means the palisade which ran along the outer edge of the top of the agger, but it very frequently in­cludes the agger also. The vallum in the latter sense, together with the fosse or ditch which sur­rounded the camp outside of the vallum, formed a complete fortification.