Castlevania: This Forever Place is a project of wishful thinking, of what might be the grandest Castlevania game that would ever be made. It is set in Dracula's Castle, which in this game is roughly modeled on parts of a university campus.
The basic area structure of the castles consists of the following:
The castle consists of four castles, actually: the First Castle, the Opulent Castle, the Infernal Castle, and the Last Castle. Each of these castles contains its own version of the areas mentioned above; the castles exist in parallel dimensions, basically.