In Japanese mythology, Ryūgū-jō (竜宮城) is the palace of Ryūjin, the dragon god of the sea. It is located under the sea. Depending on the version of the legend, it is built from red and white coral, or from solid crystal. Those that live in the palace were Ryūjin's servants, which were various creatures of the sea. On each of the four sides of the palace is a different season, and one day at the palace is like 100 years on earth. In legend, Urashima Tarō visits Ryūgū-jō.
Mythic Texts and Folktales: