Loaded with major ions — the essential minerals (Ca, Mg).
Buoyancy
Effortless float
LowHigh
Dense, salty water — you float without effort.
SodiumChloruresBrome
Onyang, in Asan City of South Chungcheong Province, is home to one of Korea's oldest and most historically significant hot springs, said to have been used by Joseon dynasty kings since the fifteenth century for recuperation, including King Sejong the Great, the inventor of the Hangul alphabet. The sodium and bicarbonate mineral waters of Onyang Hot Spring are heated to naturally comfortable temperatures and are renowned in Korean therapeutic tradition for treating chronic fatigue, digestive conditions, and musculoskeletal disorders across centuries of use. The adjacent Onyang Folk Museum and the nearby Hyeonchungsa shrine dedicated to Admiral Yi Sun-sin add substantial cultural depth to a spa visit in this historic South Chungcheong city.
Insider tip — Asan Oncheon is one of South Korea's historic hot spring towns, famous for its sodium-chloride geothermal water that has been commercially developed since the 1970s into a dense cluster of jjimjilbang and spa hotels easily accessible from Seoul by KTX express train in under an hour. The naturally warm water is often described as silky and skin-softening, making it popular for all-night gender-separated communal bathing sessions typical of Korean spa culture. Many Seoulites treat an Asan spa weekend as a restorative urban escape without leaving the peninsula. Book the premium private family pool room in advance, as these fill quickly on weekends.
