The pleasure of soaking in a secluded hot spring enveloped by the sights and sounds of nature is an experience that many in Japan love to indulge in. The country is renowned for the abundance and beauty of its onsen, or hot springs.

Many onsen users report gaining a sense of inner peace and connection with nature from such an experience. Yet engineering hot water to flow constantly from the depths of the Earth can potentially endanger fragile natural resources — first and foremost, the coveted hot-spring water sources themselves.

Hot springs are deeply rooted in Japan’s culture and history, with the country’s oldest establishment, Dogo Onsen in Matsuyama, Ehime Prefecture, thought to be up to 3,000 years old. As such, they are important pillars for local economies and the tourism industry.