I’m sorry but I completely disagree. This has nothing to do with Kairi, the castle in Radient garden looks NOTHING like this slide, but compare it to the building that Roxas and his friends sit on and eat ice cream. Not only the building but the trees surrounding it are a much better fit for the tower in twilight town. And knowing that Roxas is Sora’s nobody so technically he is a part of Sora during the first visit to deep jungle leads us to believe this place exists in someway inside of sora’s heart.