Heapstown is not as roadside a cairn as I had expected from previous reading. It’s close to the road but you’ll need to enter the field with the Sligo Heritage signpost and approach the cairn from there.
Heapstown brought to mind the 3 other cairns of similar size that I’ve visited: Ballymacgibbon, Knocknarea (Maeve’s Cairn) and Cairn D on Carnbane west in Loughcrew. Most every mention of Heapstown includes the probability of it being a passage grave, but given the Cairn D experience, and the fact that the stolen material mentioned by Gladman has so far revealed no signs of a passage entrance, I’d say the possibility is way less than 50 50.
This is a massive construction though. The kerbstones on south-east side are impressive, bulky and robust and a major job to erect in themselves. The pile of the cairn must contain the field-clearance of 100 acres or more.
I’d love to see this monument opened up a bit, some of the vegetation cut back, revealing it in all its grandeur.