Japanese gardens, Horaijima, the inaccessible island

In the ponds of the Japanese traditional gardens, there are always several islands, because the pond symbolizes the sea, and a sea without islands is simply unthinkable for the Japanese philosophy. Some of these islands are reachable by bridge, while others are completely inaccessible, left without any human intervention. The latter are most interesting, since they symbolize Horaijima, the "treasure islands", mythical places inhabited by immortals...