This is a fulacht fia, a type of prehistoric cooking site found in large numbers across Ireland, typically dating to the Bronze Age. The basic principle was simple: stones were heated in a fire, then dropped into a water-filled trough to bring it to a boil. The repeated heating and sudden cooling caused the stones to shatter, and it is precisely that fractured, fire-cracked material, mixed with charcoal-enriched soil, that now forms the mound itself.

The Canshanavoe example measures 13 metres north to south and 9.1 metres east to west, rising to a height of 1.3 metres, which places it among the more substantial surviving examples. Its opening, around 2.5 metres wide, faces west toward the river, the likely source of water for whatever cooking or processing took place here. Sheep paths have worn into the mound at the north-east and south-east, and the river is gradually eroding the outer ends of both arms. About 65 metres to the west, a separate hut site has been recorded, suggesting this was not simply an isolated feature but part of a small cluster of activity in the landscape.