The Antonine Wall lay at the very extremity of the Roman world. For a generation, in the middle of the second century AD, it was the north-west frontier of the Roman empire. Furthermore, it was one of only three "artificial" frontiers along the European boundaries of the empire: the other two are Hadrian's Wall and the German Limes. Although the Antonine Wall fits into the general pattern of Roman frontiers, in many ways it was the most developed frontier in Europe, with certain distinct characteristics. Perhaps of greatest significance is the survival of the collection of Roman military sculpture, the Distance Slabs. These record the lengths constructed by each legion and their relationship to the labour camps allow further conclusions to be made about the work of constructing the Antonine Wall.