The Complete Castle by Castle Kits, Inc is a set available at The Sims 3 Store. You can find it here. It's an unusual set, but very nice when used properly, and plenty of CAW users might like to add castles to their worlds, so it deserves some explanation because it can be a very confusing set to work with!
The first issue that many builders will have after downloading this pack is finding where all the various pieces are in the Buy Mode catalogue. There are 19 pieces in the set, and they are distributed throughout the catalogue in a very haphazard way. The best option is to create or download a Collections file for the Castle sets, but so that you can do that, Sims 3 forum user AlienND has kindly listed where each piece is in the catalogue here:
|“|| Top Of The Wall With A View > Buy Mode > Bathroom > Accents / Dining Room > Misc Decor |
Corner Wall With A View > Build Mode > Columns
When I find one, I'll add a link to a Castle set Collections file here.