The sima nö miya “Island Palace”, was an estate originally belonging to Soga no Umako (d. 626), a major power behind the throne in Yamato Japan. Following his death, it passed into the hands of the Imperial clan and was used as a detatched palace. Its was situated near the banks of the Asuka River, but not on an actual island, so the imagery used the guards’ poems is poetic conceit and not literal description.