These buildings were once essential to large estates, designed to hold blocks of ice cut from frozen ponds or rivers during winter and packed in straw or sawdust to last through the warmer months. Without mechanical refrigeration, an icehouse was the only reliable way to keep food cool, preserve game, and supply the kitchens of a wealthy household with cold drinks in summer. They were typically built into a slope or underground to take advantage of natural insulation, with thick walls and a domed or vaulted interior to slow the transfer of heat.