It measures roughly 25 metres along its longer axis and 20 metres across, large enough to fill a decent-sized garden. It looks, at first, like nothing very much. It is, in fact, the remnant of a fulacht fiadh, or burnt mound, one of the most commonly encountered prehistoric site types in Ireland and one of the least understood.

Burnt mounds are spreads of fire-shattered stone and scorched earth left behind by a process that involved heating stones in a fire, then dropping them into a water-filled trough to bring it rapidly to the boil. The stones crack under the thermal shock and are discarded in a pile beside the trough, which is where the distinctive mound comes from. These sites cluster around the Bronze Age, broadly speaking the period from around 2000 to 500 BC, and they appear in their thousands across Ireland, typically in low-lying, waterlogged ground or on slopes where a water source was close at hand. What exactly they were used for has been debated for decades: cooking is the most straightforward explanation, though brewing, hide-processing, and communal bathing have all been proposed. The site at Tulligee sits on a gentle WSW-facing slope in what is now tillage ground, and the combination of its level platform and its hillside position is fairly typical of the type.