What is an Onsen and why are they so popular?
Besides their warming and therapeutic qualities, onsen were believed to possess mystical and holy powers because of the mineral content of the geothermal spring water. On top of this, the process of creating a fire to heat water for a bath was historically quite an ordeal, so the natural hot water emanating from the earth became something that was highly valued. The Japanese were not the only bath-lovers; looking at other cultures around the world, one of the most well-known examples that comes to mind is that of the Ancient Romans, whose bathhouses can still be visited to this day.
To be certified by the Japanese government (regulations known as onsen-hou, 温泉法), an onsen must be comprised of natural spring water that is at least 25°C in its natural state and contain at least 1 of 19
