|Was the Roman Empire stopped in its tracks by the Scots? (Hint: No)|
The Internet being what it is, there are probably quite a few walls blogging nowadays. But I think it is fair to say that there are only two walls that probably deserve a blog. The Great Wall of China should, and for all I know does, have one. And of course Hadrian's Wall has enough charisma to pull off regular updates.
And the wall does indeed have a very good blog called Hadrianswallalive devoted to it.