I came across this about 18 months and would happily concede it is a pen of some sort but it has no entrance and there is a cup marked stone within 150m. The local farmer doesn't know what it is either rhttp://rockartuk.fotopic.net/c396745.html .The marked rock can be found at the same site under the name Denoon Burn . Sorry about the pic it's one of those taken from quite a distance to get it all in .