At the western edge of a working farmyard in Kilberry, County Kildare, a fragment of medieval masonry sits in the grass with an identity that has never quite been settled. Local tradition, recorded as far back as 1837, holds that this was a nunnery, its enclosing wall and fosse still traceable across the field. A fosse, simply put, is a defensive ditch used to demarcate or protect a religious or military enclosure. What survives today is a poorly preserved rectangular structure, roughly 22 metres long and just over 9 metres wide, its ivy-clad south-east gable wall and a gapped south-west sidewall standing as the last legible traces of something considerably more substantial.

The 1837 account comes from O'Conor, who co-compiled the Ordnance Survey Letters for County Kildare, and he described four portions of the nunnery walls still standing at that time, along with the ruined walls of what he called the "Cathedral," meaning the nunnery church, visible in the adjacent graveyard roughly 40 metres to the north-east. However, the religious historians Gwynn and Hadcock, writing in 1970, were sceptical of the nunnery identification. They argued that the location seemed unsuitable for a community of women religious, given that the surrounding towers and castles suggest the site sat on a main defensive line. Their alternative proposal was that the complex may have belonged to a military order, quite possibly the Hospitallers, a crusading order that held properties across medieval Ireland. Sisters could have been attached to such a house, they suggested, which would account for the persistent tradition of nuns at the site. A ruined gatehouse and a possible bawn, an enclosed courtyard typical of fortified properties, stand about 50 metres to the south-east, lending some weight to the more martial interpretation. What remains of the walls, rubble masonry averaging around 1.2 metres thick, includes a robbed-out flat-headed window near the top of the gable and two adjoining robbed-out loops in the sidewall, openings from which the dressed stone has long since been removed for use elsewhere.