Ryūgū-jō, in a classic Japanese folktale, is the mythical undersea residence of the Sea God, aka the Dragon Palace Castle.
According to the books, this fabulous palace is home to Princess Otohime. For many Japanese people, the legendary tale of the exquisite building beyond the blue sea with coral walls is as real as Godzilla sitting atop the Hotel Gracery in Tokyo's famous Shinjuku district.
When Hotel Gajoen Tokyo opened its doors in 1928, people were so awed by its richly decorated premises that it reminded them of the mystical underwater residence and nicknamed it "The Palace of the Dragon God."