See Massive Instant Structures (Castles, Towers, Gates) Only One Command Overview
This command adds in Instant Castle Structures to your Minecraft world. With this command you won’t even need to know how to build a Castle in Minecraft. These command blocks easily enable you to add in Huge Castles, Towers, and Gates to your world. If you don’t like building, then this Only One Command is great because you can instantly add awesome structures to your world. The best part is that the Instant Structures don’t even require any mods!