Heapstown Cairn

Heapstown Cairn is located immediately north of Lough Arrow, 2.1 km (1.3 mi) northwest of Ballindoon Friary.[2]

Heapstown Cairn was constructed c. 3000 BC and is believed to enclose a passage grave. It is believed to be related to Carrowkeel Megalithic Cemetery, located 5 km (3.1 mi) SSE of Heapstown. In folk tradition it was the burial site of Ailill mac Echach Mugmedóin, brother of Niall of the Nine Hostages.

One account of the cairn's construction is given in the Second Battle of Moytura. Dian Cecht, healer to the Tuatha Dé Danann, puts healing herbs into the Well of Sláine, and the Tuatha Dé Danann drink from it. The Fomorians, on a suggestion from the warrior Ochtriallach, fill it with stones to keep their enemies from using it. Thus it is known as Carn Ochtriallach "Ochtriallach's cairn."

In 1837 it stood to its full height and had a standing stone atop, but much of the stone has been removed since then for road-building.[3]

The cairn is 57 m (187 ft) in diameter and about 6 m high. There is a kerb of limestone blocks around the edge and probably a passage grave underneath.[4][5][6][7]