The Roman empire collapsed though, just like all the great powers eventually.
We have met the enemy and he is us.
Good old Emperor Hadrian. His wall didn't work very well, either..........
The Chinese built one too. Didn't work either.
The Russians built one in Berlin. I don't think the wall worked very well, but the machine gun towers were pretty effective.
Their wall was effective while it was up
I think it was really the free fire zone next to it.
Looks like this great empire is headed in that direction.
The only true wisdom is in knowing you know nothing.
And the French built the Maginot Line to ensure that Germany would not be able to invade France easily. THAT worked well...