It is easy to mistake for a natural rise in the field, barely reaching 0.45 metres at its highest point. But that curved form, opening to the east and spanning roughly 12 metres, is the signature of a fulacht fia, one of the most common yet persistently mysterious monument types in the Irish landscape.

A fulacht fia is a burnt mound, the accumulated debris of a cooking or heating method used predominantly during the Bronze Age. The typical process involved heating stones in a fire, dropping them into a water-filled trough to bring it to the boil, and repeating the cycle until the stones cracked and became useless. Over generations of use, the discarded burnt and shattered stone built up into the characteristic horseshoe shape that survives at this site near Tobercrossaun. The location follows a pattern well-attested across Ireland: fulachtaí fia are almost always found near water, whether a stream, a spring, or in this case a domestic well, and frequently in low-lying ground that would have held water readily. The flood-prone character of the spot, which might seem to argue against settlement, was almost certainly part of the appeal for whoever returned here to use it.

The mound at Tobercrossaun is described as poorly preserved, and given how slight these features are even in good condition, it would take a careful eye to read the landscape here. The horseshoe shape, orientated roughly northeast to southwest and opening eastward, is the detail most worth looking for, though the low profile means it blends easily into the surrounding grass.