The site is a fulacht fia, a type of prehistoric burnt mound that represents one of the most common archaeological features in the Irish landscape. The principle is straightforward: stones are heated in fire, dropped into a water-filled trough to bring it to the boil, and the cracked, heat-shattered fragments are then discarded to accumulate into the distinctive mound that survives above ground. What makes the Glashare example particularly interesting is the detail revealed beneath that mound, which measured roughly thirteen metres east to west and nearly twelve metres north to south.

Excavations carried out in 2006, ahead of road improvement works on the M8/N8 Cullahill to Cashel scheme, uncovered not one trough but three lying beneath the accumulated debris. Trough A was subrectangular with vertical sides and a flat base, with three stake-holes positioned at the north, south-west, and south edges, possibly indicating some kind of wooden superstructure or lining. Trough B was also subrectangular but with sloping sides and a more irregular base. The largest of the three, Trough C, was subcircular, measuring up to 2.65 metres in length, and it is from this trough that a charcoal sample was radiocarbon dated. The result placed activity at the site between 830 and 590 cal BC, squarely within the Late Bronze Age. Approximately twenty metres to the south-west, a second fulacht fia was also recorded, suggesting this stretch of the Kilkenny landscape saw sustained or repeated use during that period.