It measures twelve metres long, eight metres wide, and rises just three quarters of a metre above the surrounding ground. At its western end there is a hollow, a depression in the mound where something once sat or was dug. Without context, it could pass for a natural rise in the waterlogged ground. It is, in fact, the remains of a fulacht fia, one of the most common prehistoric monument types in Ireland and among the least understood.

A fulacht fia is essentially a burnt mound, the accumulated debris of repeated episodes of water heating. The typical arrangement involved a timber or stone trough sunk into the ground near a water source, which would be filled and then heated by dropping fire-cracked stones into it. The stones, unable to withstand repeated thermal shock, broke apart and were discarded in a heap beside the trough, building up over time into the low, horseshoe-shaped mounds that survive today. What these sites were actually used for remains debated. Cooking is the most frequently cited explanation, though brewing, hide-working, bathing, and industrial processes have all been proposed. The depression at the western end of the Killeenemer mound is consistent with the position of such a trough, now long collapsed or silted over. The proximity to a stream is entirely typical; water was the whole point, and most fulachtaí fia are found within easy reach of running water or a natural spring.