Board Thread:Castlevania Wiki General Discussion/@comment-79.103.195.131-20130319194545/@comment-453181-20130320214710

I think it was just an area to sort of give the castle some "variation", and they just stuck to it from game to game. I'm assuming the chapels in Dracula's Castle are where followers of Dracula gather to offer worship to him, since we've already seen fanatic followers of Dracula (Shaft and Barlowe). Perhaps the chapel is home to more people like them.

In Mirror of Fate, an area called the "Unholy Church" appears - according to the scrolls, apparently it was a part of the castle before darkness took hold, after which it was turned into a mockery of what it once was - perhaps there's a similar reason for its existence in the original series. But, I don't really think they were thinking about a story explanation for the area's inclusion in the game when they were creating it.