It is said that, because long ago Kameoka Basin was a big lake with beautiful, vermillion waves caused by wind, this area was called 丹のうみ(Ni-no-umi; umi means a lake in English) or 丹波(Tanba; 波 means waves in English); others say that Okuninushi-no-mikoto who is a famous god appearing in the Izumo Shinwa (Myths of Izumo) carved a valley between Kameoka and Arashiyama, and made the water flow, forming land by reclamation, and named the carved valley 'Hozu-gawa River and Hozu-kyo Gorge' after 'Mihotsu-hime,' goddess in the position of wife of Okuninushi-no-mikoto; in fact, a fault has been found that shows that Kameoka Basin used to be a lake.
太古は大きな湖であり、風が吹くと美しい朱色の波が立ったところから、このあたりを丹のうみ・丹波と呼ぶようになったとされており、出雲神話で有名な大国主命が亀岡と嵐山の間にある渓谷を切り開いて水を流し土地を干拓して、切り開いた渓谷を妻神「三穂津姫」の名前にちなみ「保津川・保津峡」と名付けたという伝説も残っており、事実、湖だったことを示す地層も明らかになっている。