Armory and weapon room to display all armor and weapons in game. Better make a piggery out back for the piggies.

I made one large castle and didn't find it particularly effective. Too much runnin around to do all the daily chores.
Have found for me armory and kitchen as 8x10 floor pieces one story with central sleeping, dining 2 stories also 8x or 10 leaves me room to enlarge, remodel without feeling like I am hoofing it half a mile to make food, repair armor. They are all connected in either a U shape or as a longhouse. Also holds couple roaming portals for exploring and one more to portal hub. You will find a system that works for you that is efficient and nice looking. May take some time though as what we think we need or like and what we really find useful don't always line up.
I want to drop in from my portal, dump off mats, repair gear, throw stuff in the furnace, make coal, ck and update consumables, make food if I need to, hit the sack in a matter of minutes. Don't want to wander around, up and down, back and forth inefficiently. But that's just me. Form follows function.