It measures around twelve metres east to west and just under eleven metres north to south, and it is composed almost entirely of burnt and fire-cracked stone. This is a fulacht fia, a type of prehistoric cooking site found in enormous numbers across Ireland, and one of the most quietly persistent features of the Irish landscape. The mound itself is the waste heap, the accumulated debris of repeated use over what may have been centuries.

Fulachtaí fia (the plural form) are generally associated with the Bronze Age, roughly 2000 to 500 BC, though some sites have earlier or later phases of activity. The usual interpretation is that stones were heated in a fire and then dropped into a water-filled trough, bringing the water rapidly to the boil for cooking meat. The cracked, spent stones were then discarded to the side, building up over time into the horseshoe or crescent-shaped mounds that archaeologists now recognise across boggy ground, river margins, and grazing land throughout the country. The Shanavoher example, with its substantial height and clear semicircular profile, is a well-preserved instance of this very common but frequently overlooked monument type.