Built atop four tall rocky islands, it is virtually desolate, inhabited only by the Queen, her daughter, and her shadowy minions. Whoever else once lived there has long since moved on, and the castle has since begun falling into ruin. The degradation of the castle reflects the state of its dying monarch. When the Queen finally dies the castle dies with her, consigned to a watery grave; The Queen's power may have been the only thing preventing it from doing so all along.

While the Queen's power may have been holding the castle together, it is Yorda's power which is most in tune with it. Within the castle there are various mechanisms, from the Idol Gates, to staircases and even invisible walkways, which only the power she possesses can activate. She shares this power with a sword that Ico eventually gains use of, and devices above the castle's main gates. The latter are part of the largest of these mechanisms, spanning three of the four islands and apparently responsible for securing the main gates. It is using this mechanism to open the way out which makes up the bulk of Ico and Yorda's journey.

The east and west islands, mirror images of each other, hold the arenas and reflectors. The reflectors are used to open the main gate by shining a beam of light the devices above it. For these beams to reach the gate however, three circular doors in each arena must be opened. Each island can be accessed by means of a massive bridge leading from the castle.