A road ran behind the wall, passed through the east and west gates of the forts and also branched off to a road leading to the milecastles and a path to the turrets.
At varying points behind the wall sat a defined earthwork barrier called the Vallum. A ditch was dug thirty feet deep and seven feet wide at the flattened bottom. The contents of the ditch were used to create a mound on either side of it about six feet high and twenty feet across. The ditch and mounds were separated by berms of about twenty-four feet in width. The entire barrier of mound, berm, ditch, berm, and mound was about one hundred and twenty feet across.
Lastly, behind the Vallum sat a Roman road called the Standgate.