龍宮城

Ryūgū-jō (竜宮城, 龍宮城; lit. "Dragon Palace Castle") or Ryūgū (竜宮, 龍宮; lit. "Dragon Palace") is the supernatural undersea palace of Ryūjin or Dragon God in Japanese tradition. It is best known as the place in fairytale where Urashima Tarō was invited after saving a turtle, where he was entertained by the Dragon God's princess Oto-hime and his minions. When Urashima returned to land after what he thought was a few days away, centuries had passed.