Two of the largest have already collapsed inward at the southern end, lending the structure an air of arrested motion, as though the monument is mid-sentence rather than finished. What survives is enough to read the original intention: a tomb oriented north to south, nearly three metres wide, with at least some of its internal architecture still legible in the landscape.

Megalithic tombs of this kind are the collective burial monuments of Neolithic communities, typically dating to roughly 4000 to 2500 BC, built from large unworked or lightly dressed stones and often covered originally by a mound of earth or rubble. At Killour, a standing slab aligned east to west survives to the north of the main chamber, measuring 1.4 metres long and 0.84 metres high, and just beyond it a small enclosed area is defined by two upright stones, one to the east and one to the west. The function of this northern arrangement is not entirely clear from what survives, but it hints at a more complex original layout than the collapsed southern end now suggests. What makes the site particularly interesting is its position within a wider prehistoric landscape. The tomb lies to the south-west of both a henge and a cairn, indicating that this corner of Mayo was a place of repeated, deliberate monument-building over what may have been many generations. A henge, to give the term some context, is a roughly circular enclosure defined by a bank and ditch, associated with ceremonial rather than defensive use, and their presence alongside tombs and cairns points to a landscape organised around ritual and the marking of the dead.

The tomb sits in pasture with a rock outcrop nearby, which is worth bearing in mind when approaching across the field. The condition is described as poor, so visitors should expect a ruin rather than an upstanding structure, but the scale of the stones that remain, and the proximity of the henge and cairn, rewards anyone willing to look carefully at what the ground is still holding.