Hot springs generated by mountains and volcanoes are an important physical feature of Japan and its history. Located on the Pacific Ring of Fire, the country is home to numerous onsens, of which over 27,000 are listed, some with histories dating back three thousand years. Even before the medieval period, their use had a powerful therapeutic and religious connection. Buddhist monks used the waters to rid themselves of physical and spiritual dirt. These springs, renowned for their spiritual submissions and medicinal properties, gained in popularity during the 16th century, particularly with wounded warriors.
Arima Onsen, one of the oldest hot springs in the country, has been famous since antiquity. Emperors and aristocrats of all eras came to bathe, and Kyoto's inhabitants even enjoyed the waters in the Middle Ages. In 1466, for example, a priest close to the shōgun spent a month there, bathing during the day and attending banquets in the evening with acquaintances such as the shōgun's painter and important vassals of powerful lords. Toyotomi Hideyoshi was certainly Arima Onsen's greatest admirer. He visited the hot spring at least nine times, and in 1585, he visited twice in a single year. In fact, he built several hot springs and a garden inside his residence, which were excavated in 1997, restored and opened to the public.