A cairn or (Irish carn) is an artificial pile of stones, often in a conical form. They are usually found in uplands, on moorland, on mountaintops or near waterways.
Cairn
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By kjfitz @ 2008-08-26 11:13:40
Parabellum
@ 2008-08-26 13:10:10
It's a cairn. Here's Ordnance Survey's topo: http://getamap.ordnancesurvey.co.uk/output1/gam/gam_print_ordsvywat-sun-176505621851.jpg