A distinctive Korean home-heating method for winter, where the floor itself warms up. What is it?

Ondol is Korea's traditional floor-heating method, historically achieved by channeling smoke and hot air from a wood or coal fire beneath the floor, and now typically achieved by circulating hot water through pipes installed under the floor via a boiler. Because the heat source is the ground itself rather than the air, warmth rises upward, which is why Korean homes are built around sitting and sleeping close to the floor and why shoes come off at the entrance to keep that warm floor clean.

A fireplace or a brazier heats a room's air directly from an open flame in one location, which is a fundamentally different mechanism than warming the entire floor surface evenly from below.

Ondol's influence runs deep into daily Korean life — even modern furniture like low tables and floor cushions, and the custom of eating and relaxing seated on the floor, trace back to a home environment built for radiant floor warmth rather than air heating.