Hadrian's Wall was a massive undertaking, but the Romans didn't stop there. For added protection, they also built the vallum - a ditch and earthwork south of the Wall. The vallum follows close beside the Wall for almost the entire length.
There are various theories about why the vallum was built. One is that it was a kind of exclusion zone along the wall. Others think it was some kind of communication route, with military traffic on one side and civilian on another. I don't think we can ever know for sure but it is fun to speculate.
Speaking of the Vallum. We stayed at the most wonderful bed and breakfast, the Vallum Lodge, which sits on the vallum! It is truly a touch of luxury on Hadrian's Wall. http://www.vallum-lodge.co.uk/accommodation.htm
Here is a photo of our rental car and myself in front of the Vallum Lodge. Notice that I'm trying to stay warm!
The Vallum Lodge is about 200 yards from the Twice Brewed Inn, which makes it very convenient to walk to dinner. The Twice Brewed has a pub quiz on Monday evenings, and is noted as one of the worst pub quizzes in England. If you get lots of answers correct and rack up the points, you would think it would be a good thing. But alas, the other teams get to play a joker on your team and reduce your point total. We know this from experience, since our team actually was pretty smart. You also get points deducted for "being clever." It may be a strange way to run a quiz, but it is a lot of fun!