A decorative castle, hunting lodge, or other not necessarily defensive large construction. The interior of the castle and two towers *should* be close to safe for survival mode if you're inclined to play so. I make no promises. Some interior decorations are done, but Schematica doesn't print decorations so you're on your own. Of course, you could just gut it and do whatever you wanted with the interior.
Might look funny in vanilla. I play in Conquest.