Dunno where you are, but it could be a number of thinks...gatepost, cattle rubbing post, megalith...or maybe just a stone (are there a lot of largeish stones 'scattered' in your region?) check out the geology of the place...maybe it's just a glacial deposition, or part of some past quarrying, or part of an old wall, farm building, cattle trough Or...Or...you get the idea...you just gotta do some research man!