Rock Wall with Barbed Wire
Rock walls can provide plenty of information about a landscape. Built out of the rocks found in the area, they often tell about the composition of the local bedrock, providing an easy place to look when the bedrock itself does not appear at the surface. Of course, stone walls were not build from the bedrock itself but from glacial till, but since the rocks in till generally moved less than a mile with the glacier, stone walls provide a decent estimate of bedrock type. Originally used as fences to keep livestock away from domestic areas, barbed wired was often added later as reinforcement.