On a west-facing slope at Murrooghtoohy in County Clare, at the leading edge of a fairly level terrace, stands a tall, rectangular cairn built from dry-laid stone. Drystone construction uses no mortar, relying instead on the careful fitting of stones against one another, and this particular cairn appears to have served a quietly practical purpose: it was most likely erected as a directional marker, possibly read by fishermen working the waters off Black Head, the headland that juts into the Atlantic at the northern tip of the Burren.

The structure was first noted as a possible cairn by Spellissy in 1980, though at that stage its nature and function were uncertain. When it was inspected more closely in 1997, its rectangular form distinguished it from the rounded prehistoric burial cairns that dot this part of Clare. That shape, combined with its prominent position on the western edge of the terrace, points toward a navigational or signalling role rather than a funerary one. Coastal markers of this kind, sometimes called seamarkes in older sources, allowed sailors and fishermen to fix their position relative to the shore by lining up visible landmarks on the land behind them. The exposed headland of Black Head, where the Burren limestone meets the sea, would have made orientation genuinely difficult in poor visibility, and a tall stone cairn in a commanding position would have been a useful reference point for anyone working those waters.