An ukdun is a kind of dwelling, originally devised by semi-nomadic and settled Yonggan people with Earthbending. Similar structures are also in use others in the Northern and Western regions of the kingdom where cold, dry winter climates prevail.
The ukdun is characterized by underground or mostly-underground construction and a circular plan, typically arranged concentrically. It also typically includes heating by means of a hypocaust and massive masonry stove-bed, and a sheltered outer area for livestock. Ukdun vary in size and complexity, and can be made to accommodate quite large households. Semi-nomadic Yoggan build different designs for different seasons; Summer ukdun built by desert-dwellers may include an evaporative cooling system.
Among the Nara clan, Yonggan people exiled to the Hanwang desert, a heating system modification similar to a "rocket stove" is popular as an adaptation to limited fuel supplies.
Ukdun may or may not include a water well, depending on the local aquifer and the availability of potable surface water.