purpose was to keep Roman Britain safe from hostile attacks by barbarians. The wall also marked the northern most boundary of the roman Empire until early in the Irish Sea, and was about 117 kilometer long.
In addition to the wall, the Romans built a system of small forts that housed garrisons of up to 60 men, along every Roman mile of its entire length. There were also sixteen larger forts holding from 500 to 1000 troop that were built into the wall, with large gates on the north face. To the south of the Wall, the Romans dug a wide ditch. Hadrian's Wall is one of the greatest monuments to the power- and limitations- of the Roman Empire.