Ancient 'Ondol' Heating Systems Discovered in Alaska What are believed to be the world's oldest underfloor stone-lined-channel heating systems have been discovered in Alaska's Aleutian Islands in the U.S. The heating systems are remarkably similar to ondol, the traditional Korean indoor heating system. The word ondol, along with the word kimchi, is listed in the Oxford English Dictionary. The ondol heating system is widely recognized as Korean cultural property. According to "Archaeology", a bi-monthly magazine from the American Archaeological Society, the remains of houses equipped with ondol-like heating systems were found at the Amaknak Bridge excavation site in Unalaska, Alaska....