It is roughly twelve metres long and twelve metres wide, a spread of burnt and fire-cracked material beneath a skin of grass, unremarkable to the eye but immediately recognisable to an archaeologist. It is a fulacht fia, one of the most common prehistoric monument types in Ireland and yet one of the least celebrated.

A fulacht fia is essentially a Bronze Age cooking site, the physical remnant of a process in which stones were heated in a fire and then dropped into a water-filled trough to bring it to the boil. The shattered, heat-reddened stones were raked out and discarded, and over time these discards accumulated into the characteristic horseshoe-shaped mounds that survive across the Irish countryside in their thousands. The Glancam example came to light during land reclamation work in the 1960s, when earthmoving disturbed the site enough for local people to notice what lay beneath. The setting is typical of the type: a stream runs to the west of the mound, and there is a possible spring to the east, placing the monument exactly where Bronze Age people would have wanted it, close to a reliable water source. That relationship between fulachta fia and water is so consistent across Ireland that the presence of a boggy hollow or a stream is often the first thing field surveyors look for when trying to locate unrecorded examples.