The site of the early medieval keeill known as St Mary's Chapel, or Keeill Moirrey, stands on a mound known as Cronk Keeillane, which is is thought to be a possible tumulus or prehistoric burial mound.  The site consists of a grass covered mound, 24.0 metre diameter and 1.6 metre high, with no surrounding ditch and which sits upon a natural mound. The northeast portions have been destroyed by a road and no trace of the chapel or burial ground enclosure remains but it seems likely that the upper mound is the remains of a bowl barrow. 


The outline of the Chapel was still apparent, and numerous stone-lined graves were found, when the public road was constructed through the burial ground.  The enclosure was described as measuring "80-50 feet" and "probably twice as large originally". Lintel graves which were certainly Christian were exposed when the road was cut and similar ones ploughed up 100 metres to the west-southwest. Oswald stated that at one time a foundation of stone walls existed but these have long been removed. Graves have been identified for over 50 metres around the barrow. Cartloads of human remains were reportedly exposed and buried again at the foot of the ridge. All graves were parallel, lying on an east-southeast to west-northwest alignment. 


At a lower level than the lintel graves, it was reported that larger stone cists were seen containing human remains. The fact of inhumation and the absence of pottery, as well as the description of these older graves, suggest that this site had been a burial place in the Neolithic.