Before mechanical refrigeration, keeping food and drink cold was a matter of architecture as much as logistics. Icehouses, common on larger Irish estates from the seventeenth century onwards, were purpose-built structures, often partly or fully subterranean, designed to store blocks of ice cut from frozen ponds during winter. The example at Rathmore in County Kildare occupies an unusually layered position in the landscape: it sits within the fosse, or defensive ditch, of what appears to be a moated site, a type of enclosed medieval settlement typically consisting of a raised platform surrounded by a water-filled or earthen moat. That a later agricultural structure was tucked into the remains of a much older one gives the place a quietly palimpsestic quality.

The icehouse itself is small, measuring roughly 4.8 metres east to west, 2.8 metres wide, and standing about 2 metres high internally. It was built from mortared rubble masonry and covered with a vaulted roof, the curving form of which would have helped retain cold air. Both the east and west gable walls have partially collapsed, and there is no longer any visible trace of a doorway, though one almost certainly existed in one of those end-walls. The interior has partially filled with clay over time. The structure is thought to have been associated with Drummin House, a property located approximately 800 metres to the south-east, which would have been the kind of substantial rural residence likely to require such a facility for preserving perishables and cooling drinks.