Some say it is a symbol of Roman power; others say the wall was a symbol of failure of the empire even when it was first built. As a child I used to believe the world ends here. I might had heard the stories about the Roman emperor who dreamt to rule the entire world and who believed he can build wall to divide this world into Romans and barbarians :)
I know it is just a misuse of the Classical past... but I just can't give this story away. The stories you weave in your heart are far more charming than the reality. And I'd say: keep weaving!
One more thing: the purpose of Hadrian's wall was at least as much symbolic as practical. And I wish we could learn to link the symbolic and the practical in everything we do.