It is easy to mistake for a natural feature, but its horseshoe shape gives it away. This is a fulacht fia, a type of prehistoric cooking site found in considerable numbers across Ireland, and one of the more quietly telling remnants of Bronze Age life in the Cork landscape.

The mound measures roughly 9.3 metres northwest to southeast and 4.5 metres northeast to southwest, rising to just 0.35 metres at its highest point. Its opening, about 2.8 metres wide, faces southwest, directly towards the stream. That orientation is not incidental. A fulacht fia typically consists of a trough dug into the ground near a water source, a hearth for heating stones, and the mound of spent, shattered stones that accumulates over repeated use. The method involved heating stones in a fire until they were extremely hot, then dropping them into a water-filled trough to bring it to the boil, a process that gradually destroys the stones and explains the characteristic scatter of cracked, fire-reddened material that survives. The charcoal-enriched soil mixed through the mound at Crumpane is the residue of those fires. Fulachtaí fia are most commonly dated to the Bronze Age, broadly speaking the period from around 2000 to 500 BC, though some examples fall outside that range. Their precise function remains a matter of ongoing debate, with cooking the most widely accepted explanation, though brewing, textile processing, and bathing have also been proposed.

The site sits in bog, which has done much of the work of preserving it, even as the edges of the mound have eroded over time. The proximity to the stream is characteristic, and the horseshoe shape, open towards the water, follows a pattern repeated at hundreds of similar sites across the island.