Burnt mounds, known in Irish archaeology as fulachtaí fia, are among the most common prehistoric monument types found across Ireland, yet they remain genuinely mysterious. They typically appear as low, horseshoe-shaped or kidney-shaped mounds of fire-cracked stone and charcoal-blackened soil, the accumulated debris of repeated episodes of heating water by dropping fire-heated stones into a trough. What that water was actually used for, whether cooking, bathing, textile processing, or something else entirely, is a question archaeologists have been arguing about for decades without resolution. That ambiguity is part of what makes each individual example worth noting.