 It had been built using about 50 stones . The barrow is sub @-@ rectangular in plan , and about 20 meters ( 64 feet ) in length . At its broader , eastern end , where the chamber is located , the monument measures 15 metres ( 50 feet ) , while at the narrower , western end , it is 12 metres ( 40 feet ) in breadth . As such , the barrow is a " truncated wedge @-@ shape " . The megalithic builders responsible for the Coldrum Stones positioned it on the top of a small ridge adjacent to the North Downs , and constructed it facing eastward , towards the River Medway . 
