This unassuming image,shows an exposed layer of worked sandstone.It has been exposed due to the erosion of the southern section of Birrens roman fort(Roman name:-BLATOBVLGIVM),by the Mein Water,a river immediately adjacent to the fort.Birrens,lay about 20 miles North of Hadrian's Wall and had a dual purpose;1)eyes and ears,as a form of early warning for enemy movements or unrest and 2)as a base camp,in its substantial annexe,for troops engaged on practice manoeuvres on the nearby Burnswark hill.
see http://www.dur.ac.uk/resources/archaeological.services/research_training/hadrianswall_research_framework/project_documents/Birrens.pdf
see http://www.roman-britain.org/places/blatobulgium.htm