Horaisan (Japanese: 蓬莱山), or horaijima (Japanese: 蓬莱島), are terms used to refer to an inaccessible island that generally is part of a Japanese garden, and are often translated as 'Treasure Mountain' or 'Treasure Island', respectively. The name comes from Horai, a Chinese island important in Japanese mythology.
Japanese gardens typically include a body of water, several islands, bridges, meditation spots, a few human structures and many types of plants. The horaisan remains unnconnected to any other part of the garden: it has no bridges nor does it have any paths or structures. This combination of inaccessibility with the island's beauty symbolizes the realm of happiness not available to mortals.[1]
In contrast to horaisan, nakajima refer to those islands which people may visit. They are connected to each other, and to the mainland, by bridges.[2]