It is the largest monument of its kind outside of the Boyne Valley. It is believed to have once been much bigger, but much of it was removed through the ages, and used to build walls and roads.
Most of the limestone kerbstones are still visible around its base.
A drawing by George Petrie in 1837 shows a standing stone on its summit, but this has long since disappeared. (To see this drawing click here.)
It is said that the cairn covers a well that possessed special healing powers. The Tuatha de Danann used this well to heal their warriors during the Second Battle of Moytura, so that they were fit, healthy and strong enough to return to the fight.
Their enemies, the Fomori, took boulders from the River Drowse and threw them into the well until eventually a huge cairn covered the pool, thus preventing the Danann from using it.
In my book, Conor Kelly and The Four Treasures of Eirean, Heapstown Crossroads is where Conor and Annalee meet the farmer who gives them a lift into Castlebaldwin after Conor spends a night under the Cairn.
This image shows the gate and stile over which Annalee levitates Conor’s wheelchair after his night spent under the Cairn.