At Knockballynoe in County Tipperary, however, that subtle difference in growth marks what remains of a burnt mound, a class of prehistoric site found widely across Ireland and Britain that archaeologists associate with the heating of water, possibly for cooking, bathing, or industrial processes. The method involved heating stones in a fire, then plunging them into a water-filled trough or pit until the water boiled; the cracked, blackened stones were then discarded into a mound nearby. Over time those mounds accumulated, characteristically dark-soiled and full of heat-shattered fragments.

The site at Knockballynoe once took the form of a small, circular mound roughly three and a half to four metres in diameter, sitting in a level area of improved pasture with boggy ground to the south, the kind of waterlogged setting that burnt mounds consistently favour. In 1993, drainage works cut directly through the location, levelling the mound almost entirely. The drain followed the line of a former field boundary, and when it was cut, burnt material appeared clearly in the exposed section. The drain runs south-east into a small stream, and the disturbed archaeology continues on both sides of it, still detectable beneath the sod. What gives the spot away now is the grass itself, which grows differently over the buried material, tracing the outline of something that machinery nearly erased.