artificial hot spring; man-made hot spring
Refers to a hot spring facility where the water is artificially heated or treated, as opposed to a natural onsen. Common in travel and leisure contexts.
This hotel has a large public bath with an artificial hot spring.
What is the difference between a natural hot spring and an artificial one?
天然温泉 is water naturally heated underground, while 人工温泉 is artificially heated or mineral-added bathwater.
Compound of 人工 (じんこう, 'artificial') and 温泉 (おんせん, 'hot spring').