How did people eat ice in the middle of summer during the Joseon Dynasty?

300 years ago in Joseon, there was no electricity or refrigerators. Ice cut from the river in winter would melt away with just a spring breeze. So, craftsmen dug into the ground and buried half of a warehouse. They covered the roof with soil and even planted grass. However, the hot air that seeped in when opening and closing the doors got trapped inside, continuously melting the ice. Finally, they flipped the concept. Instead of blocking the hot air, they made it exit on its own. They gathered hot air in recessed pockets between the arched ceiling and let it out through ventilation, and the melted water flowed out through the sloped floor. Finally, by tightly wrapping the ice with rice husks and straw, the winter ice survived until mid-summer. This is how Joseon's natural refrigerator, the Seokbinggo, was born...