蜃気楼 Shinkirō are not yōkai, but kaii—supernatural phenomenon. They take the appearance of distant, fantastic cities with tall towers and giant pagodas. Shinkirō appear out at sea on still nights, far off in the distance near the horizon. They only appear to sailors who are far from shore. Those who chase down these phantom cities never reach them. No matter how long they travel, the beautiful cities remain just as far away on the distant horizon. These mysterious illusions are caused by a legendary breed of giant clams, which breathe out fantastic images into the sky. These giant clams were known as shin, and were believed to be holy beasts related to dragons. Today, shinkirō remains a part of the Japanese lexicon as the word for mirage. While we understand the causes for this phenomenon today, its roots as a kaii are still preserved through the meaning of the kanji used to write the word: shin (clam), ki (breath), and rō (tower). According to legends, the mysterious cities that appears in these mirages are not just are illusory, but a vision of Ryūgū-jō, the mythical palace of Ryūjin—the dragon king who lives on the bottom of the sea.