Beneath it lies an icehouse, entered through a passage at the base on the north-west side. The structure above, a late eighteenth or early nineteenth century summer house, was never simply a garden retreat. It was, in effect, a decorative lid placed over a cold-storage facility, the kind of arrangement that was not unusual among the Anglo-Irish gentry but rarely survives with both elements as legible as they are here.

The summer house is square on the outside, roughly 5.7 metres on each side, with rubble stone walls covered in gravel dash render and a redbrick-lined interior. What is unexpected is the interior plan: despite the square exterior, the chamber inside is circular, about five metres in diameter, with a brick fireplace set into the southern angle and three flat-headed windows looking east, south, and west. The doorway, reached by stone steps on the north-north-east face, is flanked by a pair of blind niches, shallow semi-circular recesses, their whitewashed lime-plaster still well preserved. The whole thing sits within a walled woodland area that also served as a formal approach to Moydrum Castle, with a pathway leading north-north-east toward the castle and a now-dried pond that appears clearly on the 1837 Ordnance Survey six-inch map. Seventy-eight metres to the south stands the walled garden of the castle, and a quadrangular range of buildings to the south of the woodland was already known as Hill House by the time that same map was made.

The combination of a functioning icehouse below and a heated, formally finished room above is a small but telling detail about how these estate landscapes were used. The icehouse kept perishables cold through the warmer months by packing ice harvested in winter into an insulated underground chamber; building an ornamental structure over the mound disguised the utilitarian purpose while adding a feature to the pleasure grounds. The whitewashed niches and the circular chamber suggest some care was taken with the interior finish, even if the building was always secondary to the grander castle complex nearby.