Buried in the grounds of an estate, packed with ice cut from nearby ponds or lakes during winter, and insulated by earth and thick masonry, these structures could hold a chill well into the warmer months. The example at Castlebernard in County Cork is a particularly complete specimen, tucked into the woodland of the old demesne and built into a north-facing slope, where reduced sunlight would have helped it do its job.

The structure is circular in plan, with an internal diameter of around six metres and walls nearly a metre thick. The interior is sunken to a depth of three metres, the better to exploit the insulating properties of the surrounding earth. Above ground, a domed roof is topped by a conical slate covering, giving it the slightly anomalous appearance of a small tower emerging from the trees. The remains of a porch entrance survive to the south-east, which would have served as a buffer zone, a short transitional passage that helped prevent warm air from rushing in each time the door was opened. The whole arrangement belongs to the demesne of Castle Bernard house, the kind of Anglo-Irish estate where such infrastructure was once considered a standard domestic amenity rather than a curiosity.