Hadrian's Wall was built by the Roman Emperor Hadrian to hold back the barbarians (Scottish) from invading Roman Britain. Much of the wall has disappeared but sections are still intact and excavations are ongoing. We walked several miles of the trail along the Wall.
Mile Markers were built to mark guard posts.
At one point you can actually walk on top of Hadrian's Wall. This is my favorite photo. I enlarged it, framed it and hung it in my living room. It looks like a trail in Middle Earth. I expected to meet Frodo and Sam or a company of dwarves or at least get a glimpse of elves traveling to the sea.