Here's a knackered barrow - http://www.themodernantiquarian.com/post/33014 - the camera lens was knackered too. There's many of the different kinds of barrows at Kirkhaugh and Knarsdale. There's so many it can probably be described as a cemetery. These are the only barrows I know about in detail. Most are undisturbed by human hand. One large hilltop cairn (40 X 9m) - made of boulders, perhaps with a chamber - was crushed for roadstone last year.

I guess you would recognise a barrow by its outline and plan. The even proportions of it. There's also placename support (Barrow Bridge in Bolton) and topography. It'll 'be in the right place' aesthetically. There'll be a view from it to other monuments and sites. There's a decent photograph of one here - http://www.axisartists.org/seWORK.aspx?WORKID=23614&ARTISTID=946 - for some reason I think this one might have been a 'sky burial' platform. The views are awe inspiring from there.