No mound rises from the ground, no marker indicates that anything of note lies beneath the converted pasture and forestry plantation in this corner of County Mayo. Yet somewhere in the waterlogged soil of this field, shards of fire-cracked stone and charcoal-darkened earth survive from a period around four thousand years ago, the physical residue of an activity that prehistoric communities repeated, in this precise area, multiple times.

Burnt mounds are among the most common prehistoric monuments in Ireland, low spreads of heat-shattered stone typically associated with the repeated boiling of water, though their exact purpose remains a matter of ongoing debate. The site at Cloontumper came to light in 2002, not through deliberate excavation but during archaeological monitoring of the Lough Mask Regional Water Supply Scheme. With no visible trace above ground, the mound was identified only when burnt stone and charcoal appeared at the edge of a pipeline trench. A charcoal sample was taken and radiocarbon dated, returning a Late Neolithic date of approximately 1899 to 1681 BC. The site was not alone; a second burnt mound lies around 15 metres to the south-west, and a fulacht fia, a term often used interchangeably with burnt mound and referring to the same general class of monument, sits roughly 45 metres in the same direction, suggesting this damp ground was used repeatedly across the period.

In 2012, a private forestry plantation caused damage to the site. A north-south trench cut through the area exposed a thin layer of burnt material, around 10 centimetres deep, visible intermittently over two to three metres in the trench face, along with burnt stone fragments scattered in heaps of upcast soil. The quantities are described as meagre, and the full extent of the mound remains unknown. It is possible the trench only caught the western edge, and that the bulk of whatever survives lies undisturbed between the trench and the eastern field boundary, still buried, still unexamined.