Hadrian's Wall ... There were many walls built throughout Great Britain by the Romans, but I think this one in particular is most significant, because of the divide and rule strategy that was applied.
Around 122AD, Emperor Hadrian of Rome ordered the construction of this stone and masonary wall to protect the northern boundary of Roman Britain against the Brigantes who for the most part were farmers and based in a large territory bounded to the south by Chester and south Yorkshire and extending far north as the Clyde-Forth estuaries in Scotland.
The Wall was approximately 20'h x 8'w and extended 73 miles from the Solway Firth to the mouth of the Tyne River. It was built and rebuilt several times as Roman strategists applied their divide and rule to the Celtic population.
They exploited historical rivalries between Celtic tribes, offering alliances with one tribe in dispute with another. They divided the people, created territorial boundaries that have endured into the present. A few sections of The Wall remain standing today.