It does seem like there's two Castles in the original Castle, but the "Abandoned Castle" in CoD seems to have elements from both original Castles, so it still doesn't make sense.
http://www.vgmuseum.com/mrp/entrance.htmDon't have any "good" theories, but considering that the "Abandoned Castle" is still standing before "Dracula's Castle" is risen, maybe it's a Castle that's been there for centuries that originally has nothing to do with the "Demon Castle". When Dracula's Castle is created or regenerated, it is used as a template, since it's the nearest Castle to Dracula's Castle. When the Demon Castle crumbles, this "real" one remains and can be used by Dracula's forces until the Demon Castle returns. Maybe it's Dracula's original castle that he created and lived in for a while, but he later tapped into demonic energy that allowed him to "summon" the "Demon Castle" nearby, so he "abandoned" this one and started using the new demonic one?
Games featuring the Abandoned Castle? (was standing at the beginning of the game and didn't dissolve at the end):
- Curse of Darkness (Isaac and monsters hung out here)
- Order of Shadows (called the "mansion", Dracula's Castle didn't materialize until Dracula was revived)
- Simon's Quest (it's "abandoned", but not pulverized)
- Bloodlines (it's run down, but not completely destroyed and has the same mechanical boss)
Games featuring Dracula's Castle (patterned after the Abandoned Castle, often "raised" at the beginning or middle of the game, crumbles at the end):
- Legends
- Dracula's Curse
- Curse of Darkness (revived near the end)
- The Adventure and Belmont's Revenge
- Order of Shadows (raised when Dracula is raised, but mysteriously doesn't crumble at the end)
- Castlevania (looks "exactly" like the Abandoned Castle, but destroyed when Dracula is killed)
- Harmony of Dissonance (came into being when Maxim "second" soul was created)
- Rondo of Blood etc
- Symphony of the Night (castle "appeared" because of Richter and showed Maria the way)
- Order of Ecclesia (castle "appears" when Dracula resurrected and then dissolves)
- Legacy of Darkness and Castlevania 64 (crumbles at end of C64)
- Aria of Sorrow (sealed in an Eclipse)