When archaeologists visited in April 1992, they found a low, crescent-shaped mound, roughly twelve metres east to west and eleven metres north to south, rising less than half a metre above the surrounding ground. At its centre sat a waterlogged hollow, and on the mound itself were the telltale signs of a fulacht fia: cracked burnt stone and blackened earth, partly obscured by a covering of rushes.

A fulacht fia is a type of ancient outdoor cooking or processing site found widely across Ireland and Britain, typically consisting of a horseshoe-shaped mound of fire-cracked stone beside a trough or pit that could be filled with water. Stones were heated in a fire and then dropped into the water to bring it to a boil, allowing meat to be cooked or other tasks, possibly including textile processing or bathing, to be carried out. The sites are generally associated with the Bronze Age, though their exact function has been debated by archaeologists for decades. At Kilmacshane, the crescentic form of the mound and the waterlogged hollow at its centre fit this pattern closely, and the location in low-lying, seasonally wet ground is typical of the type. The site sits overlooking woodland to the north, with a drain running immediately north of the mound, suggesting the landscape has long managed its excess water in various ways.

When researchers returned to the site in April 2008, they could not locate the monument at all. Dense briar growth had apparently swallowed whatever remained above ground. The site is not alone in this corner of Galway: three other fulachta fia have been recorded nearby, suggesting this stretch of marshy ground was a repeatedly used landscape in prehistory, visited by people who knew how to read wet terrain and turn it to practical ends.