Castles, are they your base or just the most important part?

So I have no idea if this decision is already set in stone or not, but how will castles work in this game? Will they be your base for all intents and purposes, or will they be in the back of your village/base and be the ultimate objective of any game?
If castles are your base, will they be able to upgrade themselves? For instance, player A has acquired x amount of resources, and they want to upgrade their castle. So they zoom back to their base and select their castle and are given set options (say, upgrade defenses, upgrade blacksmith, upgrade grain storage, etc...), after choosing one, y amount of time passes and then *bam*, their castle expands with their new stuff. If that is how this game progresses, can the size of the castle expand with the upgrade? Small castles that are shinier aren't very fear inspiring.
Alternatively, if castles are just at the back of your village/base, will the castle basically be just a giant fort with defenses, while everything else gets upgraded?
Oh, and since this game has castles in it, it must have walls, do not disappoint. |||Vlog number 8 or 7 had a sneak peak at some of the walls in the game, and from those 5 seconds i'm going to cautiously guestimate that "walls" will be more like a part of the map in certain conditions. Meaning the castle & walls aren't actually buildable but static parts of the map. That is my cautious guess at this points.
Feel free to correct me GPG. *wink*|||Rome: Total Dragons|||_PINK|||Solar|||OrangeKnight|||_PINK|||Total War sucked after Medieval, frankly.|||DeadMG|||Headless