This is my scaled diagram of the cathedral I'm planning. That's right, it's not a train, I'm finally going to build a true, large castle MOC.
The floor plan you see here is a modified version of St. Patrick's Cathedral in New York City. While the layout will be similar to that, the architecture will look more like Chartres Cathedral, with a nice Gothic look with flying buttresses. It's not going to be the most ornate cathedral ever built, but it will be a nice size - 2x4 green baseplates. I've chosen this size because I'd like to take it to shows, and anything larger would either be hard to move or incorporate (plus smaller is cheaper). I hope to be able to design it to break into 3 sections (I was hoping for four but looking into it it just won't work out that way). I'm NOT going to be striving for historical/period accuracy - it will ultimately be a design of my imagination.
I already know I'm going to need to acquire more arches and slopes in grey, and a huge number of transparent colored bricks and plates for the windows. However, for everything else I plan to finally tear apart Ulmaris Castle and the Temple of Formeathan. Ulmaris Castle has been built for four or five years now, and for the last two it's been boxed up in storage. The Temple of Formeathan is even older - built in 2004, and I've never even taken official pictures of it (I will fix that before the end, though).
Worry not, Ikros fans. I've pretty much figured out trying to shoehorn Ulmaris into the story as I was attempting is a big reason why I couldn't get up the want to continue the story. As for the Temple, I have plans to build something different (hopefully better) for the story that will actually make it better (the story has Garadaine seeking out the Oracle, who was going to live in the Temple of Formeathan. Since the temple would have had to have been only about 30 years old, actually much younger), I can't see how the Oracle would have been all that famous after only that short of time. An older, more dilapidated temple will fit the bill much nicer).
I'll be posting work in progress photos in my Flickr gallery as time goes by. I'll add to this thread, too, if y'all are interested.
--Tony
. I also like to build castle churches and am presently building one, only at a horrible snails pace so it could ba awhile 
. Your plan looks great, and having seen St. Patricks I'd sayt thats a great inspiration. Hope to see more Ikros aswell btw.
I don't really plan to use a lot of flextubing in my cathedral (that might change, I don't know), but I've plenty of 1x1 round bricks. The 20+ 3x3 plus shaped columns of the Temple of Formeathan are comprised entirely of 1x1 round bricks. 
