The Atreb|at|es were the "settlement people". Their tribal lands centred on Arras and extended south to the Authie that separated them from the Ambiani.

The frontier with the Viromandui to the south lay approximately on the boundary of the Nord Pas-de-Calais region untill it crosses the A2 motor way. From there the frontier ran north-east with the Nervii to the east, touching the source of the Sensée to reach the Scarpe at Douai. From Douai the border ran east to the Escaut slightly north of Escautpont.

After following the Escaut north for a short distance, the frontier turned north-west aligned with the present Franco-Belgian frontier for some distance and continued in a straight line to the Lys at Armentieres.

Following the Lys to Estaires with the Menapii to the north, the frontier turned south-west directly to the springs of the Canche and from there, south-east to the source of the Authie north of Thièvres.