A fulacht fia is a type of prehistoric cooking or heating site, typically identified by a horseshoe-shaped mound of fire-cracked stone built up over repeated use, usually beside a water source. The example at Cahircalla Beg is not particularly famous, but it is quietly remarkable: archaeologists estimated it contained roughly 400 tonnes of burnt stone, and it measured nearly 17.5 metres at its widest. At its centre sat a rectangular stone trough, approximately 1.8 metres long and less than half a metre deep, into which heated stones would have been dropped to bring water to the boil.

The site came to light in 2004 during excavations ahead of construction of the N18 Western Relief Road, and radiocarbon dating revealed a surprisingly complicated history. The earliest activity here dates to somewhere between 2550 and 2300 BC, when a spread of heat-shattered sandstone was laid down. A second spread followed around 1440 to 1280 BC, this time composed predominantly of limestone, reflecting what was readily available underfoot. Then, after a gap of roughly a thousand years in which nothing was deposited, the main body of the mound accumulated between the 12th and 9th centuries BC. Neither of the two earlier phases showed any evidence of the stone trough, which appears to belong to the later, more substantial period of use. A small quantity of burnt mammal bone was also recovered, though not enough to identify the species. Broadly similar spreads were found during the same excavations roughly 220 metres to the north and west, suggesting this corner of Clare saw repeated, if intermittent, prehistoric activity across more than a millennium.