Castle Oblivion is a large building with 25 floors, 12 going down, 12 going up, and 1 in the middle, decorated with a floral design, with many odd structures jutting out from it. The castle has a mysterious aura to it that weakens anyone who enters it except for Organization XIII, who had come across this mysterious building and seized it for their own. This energy also allows Castle Oblivion's floors can be transmuted into different forms and layouts through extreme concentration of an individual's memories, though they are often incomplete and without their natural inhabitants.