i dont know if its in twilight town or the world that never was
Its definitely in The World That Never Was. Naught’s Skyway is an area in the Castle That Never Was, in The World That Never Was. It is a small outside path in a high section of the castle. This is where Mickey finds DiZ, who is revealed to be Ansem the Wise, being attacked by Nobodies. After they are defeated, the two walk off with Ansem’s encoding machine. Sora and his companions pass through here in order to find King Mickey and Ansem the Wise.
Its the area right after you have defeated Xigbar (The Hall of Melodies 1F)
The World That Never Was
The Castle That Never Was