To the untrained eye it might pass for a natural undulation in the ground, but it is in fact a fulacht fia, one of the most common yet least understood monument types in the Irish landscape. Roughly oval in plan and measuring around 5.7 metres east to west and 4.5 metres north to south, with a height of just 0.6 metres, it is modest in scale but represents a practice repeated thousands of times across prehistoric Ireland.

A fulacht fia is essentially the debris of an ancient cooking site. The typical interpretation is that stones were heated in a fire and then dropped into a water-filled trough, bringing the water to a boil and keeping it there long enough to cook meat. Over repeated use, the stones would fracture and become useless, and the cracked, fire-reddened fragments were piled to one side, forming the horseshoe-shaped or oval mounds that survive today. The proximity of this example to a stream is entirely characteristic; access to water was a practical necessity, and fulachta fiadh are almost invariably found in wet, low-lying ground near a water source. The broader area around Frenchfort is evidently well-suited to the type: a second fulacht fia lies roughly 150 metres to the east-northeast, suggesting repeated or sustained activity in this part of the landscape during prehistory, most likely in the Bronze Age.