This one, in the townland of Tirnaneill in Co. Monaghan, only came to light because a road improvement scheme along the N2 between Monaghan and Emyvale required archaeological testing before work could begin. What the excavation uncovered was modest in scale but precise in its age: a single isolated pit, measuring 1.72 metres by 1.46 metres and no deeper than 27 centimetres, sitting quietly in a low-lying stretch of drumlin country.

The pit belongs to a category known in Irish archaeology as a burnt mound or burnt pit, the remains of a process in which stones were heated and then used, most likely, to boil water in a trough or pit. It is a type of site found widely across Ireland and Britain, typically associated with the Bronze Age, though they continued in use for centuries. Radiocarbon dating of an alder fragment recovered from this example returned a date of 1022 plus or minus 29 BP, placing it somewhere between AD 902 and 1147, which puts it firmly in the early medieval period rather than prehistory. That date range spans the late Viking Age and the decades leading up to the Norman arrival in Ireland, a period of considerable upheaval, though what domestic or communal activity this particular pit served remains unknown. The use of alder, a wood that grows readily in wet ground and was commonly harvested in Ireland, fits the low-lying, drumlin-edged landscape in which it was found.