I followed the path along the northern edge of the Wall ditch,for almost a mile,through thick forest.At this change of direction,the ditch had become clogged with detritis,probably, dead trees and annual deposits of leaves.The Wall,at this point is the sandy slope to the lhs of the shot,whilst the lochan is the wall ditch. see http://www.google.co.uk/imgres?imgurl=http://www.undiscoveredscotland.co.uk/falkirk/roughcastle/images/roughcastle-450.jpg&imgrefurl=http://www.undiscoveredscotland.co.uk/falkirk/roughcastle/&h=338&w=450&sz=57&tbnid=acnFlLrR_bfqOM:&tbnh=107&tbnw=142&zoom=1&usg=__8TS_en4F4UhMgAGIdOdtyoRzy2g=&docid=istNh933KmAx2M&sa=X&ei=vpIhUrCrIOq00wXvv4C4DQ&ved=0CFsQ9QEwAQ&dur=10227